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Free Software Licenses:
A General Overview*

By Shannon Peevey,  UNT Central Web Support

The SCO Group (SCO) (Nasdaq: SCOX), the owner of the UNIX operating system, announced today that it has filed legal action against IBM (NYSE:IBM) in the State Court of Utah, for misappropriation of trade secrets, tortious interference, unfair competition and breach of contract. The complaint alleges that IBM made concentrated efforts to improperly destroy the economic value of UNIX, particularly UNIX on Intel, to benefit IBM's new Linux services business. (The SCO Group)  

The announcement above, made on March 7, 2003, began the “march” of the SCO Group, formerly known as Caldera, against the Linux kernel. The free software, or open source, movement, led by the Free Software Foundation and the Open Source Initiative, were to this point sure in step, and purpose, in the creation of software that would be licensed under permissive licenses which protected the rights of end users everywhere. With this announcement, however, many Free Software leaders needed to step back and assure the rest of the technology industry that these allegations of “intellectual property” appropriation were completely unfounded. 

Six months later, it seems that the SCO Group might be foundering in its claims, and that the free software licenses, and in particular, the GNU General Public License, have served their purpose in providing a bulwark of protection for free software users and developers.  But, what have free software developers learned from this situation?  Have they learned anything?

As many reporters point out, the Free Software movement is facing the reality of becoming involved in big business, and a part of that reality is the importance of being aware of copyright laws and licenses that are available to help protect software from litigation.  In this article, we are going to take a look at the reasons behind the free software movement, the organizations that lead it, look at some similarities that permeate all open source licenses, and then compile an overview of ten popular free software licenses that are used in many free software projects, as well as, listing the most important differences between these licenses.  By doing this, we will be able to look at the most popular licenses that are being used to protect free software, and create a repository of licensing information, so that project managers will have an easier time in choosing a license that is appropriate for their projects.                    

But first... 

We need to discuss the Open Source Initiative, the Open Source Definition, and the reasons for its creation.  The Open Source Initiative was a brainchild of Eric Raymond, a leading defender of free software tenets, and Bruce Perens, head of the Debian GNU/Linux project, and was created in an effort to promotes the open source development process to businesses. They believed that the open source development model “produces better software than the traditional closed model”, and have taken it upon themselves to set the standards by which outsiders can measure the “openness” of a license or a project. (Open Source Initiative index.php)  They have done this by publishing the Open Source Definition, which is a list of ten criteria which must be met for a license or project to be called “Open Source”.  These criteria are (Open Source Initiative docs/definition.php):

1. Free Redistribution

- The license must allow for free distribution of a program and any derivatives of said program.  This is to protect from the temptation to ever license a project in a way that would force others to pay royalties for the software.

2. Source Code

- All software must provide easy access to the machine-readable source code.  (Either through inclusion with the software, or from a central repository that is easily accessible).

3. Derived Works

- The license must allow for redistribution of the original version of the software, or derivatives thereof.

4. Integrity of The Author's Source Code

- The license must provide for a mechanism by which modifications can be traced.  (This is to protect the author's reputation).

5. No Discrimination Against Persons or Groups

6. No Discrimination Against Fields of Endeavor

7. Distribution of License

- All redistributions of a product, or derivative thereof, must be accompanied with the same rights as the parent.

8. License Must Not Be Specific To a Product

9. License Must Not Restrict Other Software 

10. The License must be technology-neutral

If a license is submitted to the Open Source Initiative, and the Open Source Initiative staff find that license to be legally acceptable, by meeting   the requirements of the law, plus these criteria, they then add it to their list of Open Source Initiative-approved licenses.  (There are now 45 OSI-approved licenses).

The reason behind the creation of the Open Source Initiative, was the fact the founding members wanted to move away from the connection of the open source development model, with the term “free software.”  “Free Software” is the term that Richard Stallman and Free Software Foundation uses when referring to open source, or to them, free software. This is because both “open source” and “free software” “convey different ideas”. (Free Software Foundation /philosophy/free-software-for-freedom.html)  “Free software is a matter of the users' freedom to run, copy, distribute, study, change and improve the software”, (Free Software Foundation /philosophy/free-sw.html) whereas “open source” means “You can look at the source code.''  (Free Software Foundation /philosophy/free-software-for-freedom.html#relationship

Eric Raymond and crew decided that the term “free software” was hindering the movement's ability to be accepted by big business in general. Therefore, when Netscape decided to release its browser's machine-readable source code to the public in 1998, Eric Raymond, in conjunction with many top free software programmers, came up with the term “open source”, and started the Open Source Initiative to promote the term and the software that it pertains to.

To date, they have been very successful in generating interest with big business, as Oracle, IBM, and all of the major hardware vendors either support or have contributed to “open source” projects. (As an aside, it must be mentioned that the Free Software Foundation and the Open Source Initiative still work together on many things.  It is interesting that when SCO began spreading rumors about Linux and its alleged breach of SCO's intellectual property, the “open source” community, once again, looked to the Free Software Foundation as its compass...)

Second...

We need to discuss the similarities among all of the Open Source Initiative approved licenses.  Since the Open Source Initiative has an openly available set of criteria, and that criteria must be met for a license to become OSI-approved, there are obviously going to be similarities amongst all of the licenses that are going to be viewed in this paper. 

These similarities can obscure the uniqueness of each license, and it may seem apparent that there is probably not a need for a large number of OSI-approved licenses.  But, in fact, there are already 45 such licenses, and many more are being submitted to the OSI for approval at the present time. 

Why is that?  For one, these licenses are able to address issues that might be of particular importance to a certain sector of software usage, or development.  Another reason, might be that these licenses might be used as form of free advertisement for a particular group or individuals, and finally, the new licenses might address newer issues that were not apparent at the time when the seminal licenses were written.  Needless to say, the licenses that will be reviewed in this paper are considered to be OSI-approved, and therefore, have these common threads (The Open Source Initiative docs/definition.php):                   

1. The “user” has permission to use the software for any reason, make modifications and redistribute the software in original or modified versions, if certain requirements are met.

2. The license must contain a notice that notifies a “user” that the software should be considered “As Is” and is without warranty.

Even the most simple licenses, such as the BSD License, from University of California at Berkeley or the MIT License, contain these important elements, and, from a historical note, these points are directly descended from the GNU General Public License, which was the first real “copyleft” license, and is still the most strict, of all free software licenses.

Third...

It is important to understand the differences between OSI-approved licenses.  To do this, we are going to discuss ten specific licenses that are OSI-approved, including the GNU General Public License, the BSD License, and Apache Software License.  In doing so, the author hopes to create a broad overview of Free Software/Open Source licenses for the interested project coordinator, and help them to decide which license will fit their particular projects goals and needs.

The first license that we are going to look at is the Open Software License Version 1.1.  This license was written by Lawrence E. Rosen, general counsel for the Open Source Initiative, and submitted to the Open Source Initiative for acceptance as a license that meets all of the tenets of the Open Source Definition. (Open Source Initiative /docs/certification_mark.php#approval)  This license is currently one of the most complex licenses that we will look at on this list. The reason being that Mr. Rosen has tried to add components to this license that address new issues, such as patent licensing, and also uses legal language that is an attempt to deal with legal holes that might appear in less carefully worded licenses. This license contains our two common threads (The Open Source Initiative docs/definition.php):

1. The “user” has permission to use the software for any reason, make modifications and redistribute the software in original or modified versions, if certain requirements are met.

2. The license must contain a notice that notifies a “user” that the software should be considered “As Is” and is without warranty.

As well as (The Open Source Initiative /licenses/osl.php):

1. Grant of Patent License

-The “Grant of Patent License” clause gives the user rights to any patented materials that were placed in the software by the previous distributor.  (Distributor meaning the person from whom a user has obtained an open software-licensed product.) 

2. Exclusion of License Granting

-Excludes the user's rights from anything that is not expressly stated within the contract.  (Excludes users rights from any trademarks, patents, or copyrights, that the licensor holds, but is not included in the current product).

3. Acceptance and Termination

- This clause actually states that you show your agreement to this license if you redistribute the product, limited to the terms of the license.  If any of these terms are omitted or broken, then the user's rights are terminated immediately.

4. Mutual Termination for Patent Action

- This clause terminates all rights given to a user under this license, if a user files any sort of litigation against the Licensor of the product.

5. Jurisdiction, Venue and Governing Law

-States that any litigation over product must take place in the jurisdiction that the Licensor resides in.

6. Attorneys Fees

-If a user is found to be entitled to any damages that occurred under the license, they are entitled to recovery of costs and damages, plus attorney fees.

7. Miscellaneous

- Protects the license, and claims that any part of this license that is found to be non-enforceable, does not void the license, but only the part that is unenforceable.

Though a very comprehensive license, the Free Software Foundation warns of incompatibilities with the GNU General Public License, and difficulties in discerning if the “copyleft” compatibilities “really work”.  (Free Software Foundation /licenses/license-list.html#SoftwareLicenses

But what is “copyleft”?

Now, we must take a moment and discuss the term “copyleft”, and why we will be using this term so frequently. First of all, “copyleft” is a term that was coined by Richard Stallman as a reference to the way in which the GNU General Public License reverses the intended purpose of the copyright license.

Copyright licenses, up to this point, had been used by Licensors as a way of restricting the rights of users in an effort to protect a part of their “intellectual property”. What the GNU General Public License did, was “to guarantee your freedom to share and change free software--to make sure the software is free for all its users”. (Free Software Foundation /licenses/gpl.html)  It did this by taking advantage of the existing copyright law, and wording the license in a way that gave end-users the same rights as the Licensor, allowing the end-user to modify, redistribute, and make use of software that was licensed under the GNU General Public License as if it were their own.  Needless to say, this has had huge ramifications on the computer industry.  (Many of which are only now being felt). 

As was mentioned before, the GNU General Public License was the first true “copyleft” free software license, and remains the most strict. To understand this, we must see the criteria that a true “copyleft” license must meet. A true “copyleft” license must meet the following four criteria (Free Software Foundation /philosophy/free-sw.html)

1. The freedom to run the program, for any purpose (freedom 0).

2. The freedom to study how the program works, and adapt it to your needs (freedom 1). Access to the source code is a precondition for this.

3. The freedom to redistribute copies so you can help your neighbor (freedom 2).

4. The freedom to improve the program, and release your improvements to the public, so that the whole community benefits (freedom 3). Access to the source code is a precondition for this.

Plus  (Free Software Foundation /copyleft/copyleft.html):

1.Copyleft is a general method for making a program free software and requiring all modified and extended versions of the program to be free software as well”.

Though we have already seen the first four tenets in our “Open Source Definition”, the final tenet for true “copyleft” brings many people to pause.  This tenet means that your software that you have created cannot be included in any package, or aggregation of packages, (except for distribution media), that are proprietary, or could become proprietary at some point in the future!  Though many computer enthusiasts find this to be acceptable, and even beneficial, many companies find this to be the difficult hurdle to overcome when studying the “open source” solution.  How is one supposed to maintain a competitive edge, if all software one distributes, is open for all to see, and can be redistributed by anyone else...? 

It is not appropriate to tackle this question here, but one can search for information on Cygnus Solutions, MySQL AB, and Red Hat, Inc., to find more information on the business possibilities that are available using the open source model.  Needless to say, this “copyleft” idea is the purists' idea of free software development, and has proven to be a very effective tool in gathering developers, etc. around successful tools, such as the Linux kernel, the GNOME desktop, and the MySQL database server.

Now...          

that we have discussed the Free Software Foundation and the GNU General Public License, it seems appropriate to cover the specifics of the GNU General Public License. The GNU General Public License, or GPL, is the most popular free software license. This license was created in response to an attempt by Unipress Emacs to stop Richard Stallman from distributing his version of Emacs, a text editor, which contained bits of Unipress Emacs code.  (Li-Cheng Tai)  He wanted to create a way in which his software, (as the original author of Emacs), would never be restricted again. This effort eventually became the GPL.  The GPL is the standard by which all other free software licenses are currently measured, and hence, it was the first to contain our two original threads (The Open Source Initiative docs/definition.php):

1. The “user” has permission to use the software for any reason, make modifications and redistribute the software in original or modified versions, if certain requirements are met.

2. The license must contain a notice that notifies a “user” that the software should be considered “As Is” and is without warranty.

It also requires that all software that is licensed under the GPL needs to be redistributed with the GPL, that all derivations must include notice of changes and licensed under the GPL, and all versions must contain a disclaimer of warranty.  In a thoughtful clause, the GPL does define aggregation, and claims that aggregation on distribution medium does not force all of the software on the medium to be licensed under the GPL. Finally, it imposes a measure that forces the distributor to make the machine-readable source code available.

Next, we need to look at the second most popular license under which free software is licensed.  The BSD License.  This license was created in 1979 by the University  of California at Berkeley in order to protect its own version of AT&T Unix, the Berklee Software Distribution, or BSD.  (The FreeBSD Project)  It was the very first free software license, but is not considered “copyleft”.  It is a very permissive license, that allows for a user to do anything with the software they receive, even sell it, without access to the source code.  The BSD License is very short, allowing free redistribution of software with only three requirements (Open Source Initiative /licenses/bsd-license.php):                  

1. Retain the copyright notice, the list of conditions and a disclaimer of warranty with distributions of source code.

2. Retain the copyright notice, the list of conditions and a disclaimer of warranty with distributions of binary executables.

3. The names of the <organization> which originally created the software cannot be used to endorse any modified product without written permission .

The Apache Software Foundation has been one of the great success stories in free software.  Their HTTP server, the Apache Web Server, has dominated the web server usage in all markets for the past six years.  And, as of August 2003, it is being used in 64% of all internet websites, with Microsoft IIS taking up 24% of the rest.  (NetCraft)  Many attribute this success to its business friendly license, the Apache Software License, which, as of version 1.1, users must (Open Source Initiative /licenses/apachepl.php): 

1. Retain this Copyright notice.

2. Distribute the binary executable with this copyright and license in the documentation.

3. The end-user documentation must contain:

- “This product includes software developed by the <organization name> <URL>.”

4. The copyright holder cannot be used to endorse software without written consent.

5. The product derivatives must not have <organization> in name without written consent.

6. The disclaimer of warranty.

This license is OSI-approved but not considered “copyleft”, because it can be combined with proprietary software. 

Another success story for free software is PERL.  The Practical Extraction and Retrieval Language was created by Larry Wall in mid-1980's, in a reaction to system administrative needs that were not being met by other programming languages.  With a linguistics background, Larry Wall wanted to create a programming language that would allow programmers to program in a way that was convenient for them, and to have access to advanced text manipulation capabilities.    Needless to say, he succeeded.  PERL is one of the most popular and portable languages in the world.  Actually, an interesting side note is that PERL was once the only language that you could use to administer a Microsoft Windows server.

PERL is now being released under the GPL, but it was initially released under the Artistic License.  Because of the prevalence of PERL, it seems important that we take a look at this alternative license.  (As a matter of fact, your PERL software can be released under either the GPL or the Artistic License).  The Artistic License contains our two common threads, and the following limitations (The Open Source Initiative /licenses/artistic-license.php)

1. Users may copy if they include the original copyright and associated disclaimers.

2. Versions that are modified with bug fixes and port fixes can still be considered the “Standard Version”.  (“Standard Version” is the version that is considered to be authoritative).

3. Users may modify the “Standard Version” if they include notification of the time and date of the changes AND:

- they make the modifications freely available, or;

- they only use the modified application within their organizations, or;

- they make other distribution arrangements with the copyright holder.

4. They may distribute executables if:

- they include instructions on how to get the “Standard Version”, or;

- include the machine-readable source code, or;

- make other arrangements with the copyright holder.

5. They may charge for:

- Copying fees

- Support services

- If the user includes the licensed software with a commercial project, AND does not advertise the licensed software as their own.

6. Input and output from programs in licensed under this Artistic License does not fall under the copyright of the license.

7. The name of the copyright holder may not be used to endorse or promote products without written consent.

8. Disclaimer of warranty.

Though this license is OSI-approved, it again fails the “copyleft” test.  This is because of the third clause in section five, which states, “If the user includes the licensed software with a commercial project, AND does not advertise the licensed software as their own”.  This essentially allows a distributor to include an Artistic Licensed software into a proprietary application, which could have restrictive licensing and force the removal of the Artistic Licensed software from the realm of free software.

Lawrence E. Rosen, the author of the Open Software License, has also authored the Academic Free License.  The Academic Free License is complex, and mirrors the Open Software License in many ways, including the “Mutual Termination for Patent Action” clause that causes the “copyleft” problems with both licenses.   It differs from the Open Software License in the fact that it does not include the “Grant of Patent License” clause, or either the “Jurisdiction, Venue and Governing Law” and the “Attorneys Fees” clauses.  This license is not “copyleft”.

The MIT License, which iscopyleft” compatible, is a simple license that is very similar to the BSD License.  It only contains the two common threads that run through all of the licenses...  That is all.  (Actually, the author wonders at the compatibility of this license with the GPL...  But, greater minds than his have pondered this).

The Common Public License is a complex license that is not “copyleft”.  It seems to have been written by IBM, and is OSI-approved.  This license grants (The Open Source Initiative /licenses/cpl.php): 

1. non-exclusive, royalty free rights to use Common Public Licensed software.

2. Non-exclusive, royalty free patent licenses.  (Much like the Open Software License).

The license imposes the following limitations on distribution (The Open Source Initiative /licenses/cpl.php):

1. Must comply with terms of this license agreement.

2. Distributed product's license agreement must:

- disclaim liability of contributors

- states that provisions to license are limited to that contributor

- makes source code available with this agreement

3. Contributors must identify themselves as the originator of their contribution.

Finally, this license addresses some issues with commercial distribution, such as (The Open Source Initiative /licenses/cpl.php): 

1. A contributor that includes a Common Public Licenses program in a commercial offering, cannot do it is such a way as to hinder any future contributor.

2. If the above point does happen, then the offending contributor must defend and indemnify all other contributors.

As you can see, this license is very complex, and it does address issues that would be of importance to the business world.  But, it does “requires certain patent licenses be given that the GPL does not require”, therefore, the problem with “copyleft”. (Free Software Foundation /licenses/license-list.html)

Python, like PERL, is a so-called glue language.  Python was created by Guido van Rossum in 1990.  (Python Software Foundation).  It has an object-oriented programming foundation, which means that it is easy to write small components for a program, and put them together to do something greater, is strongly-typed, meaning that indentation matters within the Flow of Control of a program, and is fairly easy to learn, like PERL.  This programming language has become more and more popular, and is now the equal to PERL.  It is used in the dynamic content web server, Zope, and allows modules to be written in other languages, such as C or C++, and then have them directly accessible to the python script.  The license under which it was distributed, and which is OSI-approved is not “copyleft”, but the newer versions of the Python License, or the CNRI Python License, are.  The OSI-approved license that we are going to look at belongs to Python 1.6b1.  This license basically states that this license is an agreement between the Corporation for National Research Initiatives and the end-user.  It grants you (The Open Source Initiative /licenses/pythonpl.php)

1. non-exclusive, royalty free rights, if:

- this license is included in all derivative works

- include the following text  “Python 1.6, beta 1, is made available subject to the terms and conditions in CNRIs License Agreement. This Agreement may be located on the Internet using the following unique, persistent identifier (known as a handle): 1895.22/1011. This Agreement may also be obtained from a proxy server on the Internet using the URL: http://hdl.handle.net/1895.22/1011”. (Or, derivations based on your needs).

Limitations that are imposed on a user are (The Open Source Initiative /licenses/pythonpl.php):                    

1. that changes must be noted in modified distributions.

2. That the license is terminated upon breach of agreement.

3. That the license is under the jurisdiction of  the State of Virginia, and does not constitute any special permissions or business partnerships, that are not otherwise explicitly mentioned in this license.

It is the final section, Section 7, of this license which makes this license incompatible with the GPL, and therefore, not “copyleft”.

The final license that we will look at in this paper, is the Zope Public License Version 2.0. This simple license is compatible with the GPL, but is not “copyleft”.  This license basically states that you can redistribute the licensed program in either machine-readable source code, or binary executable, if (The Open Source Initiative /licenses/zpl.php)

1. you retain the copyright, this list of conditions, and disclaimer.

2. the licensor cannot be used to endorse products without written consent.

3. That you notify end-users of modifications that you make to the program.

In an interesting move, based on the brevity of the license, the Zope Public License revokes the rights to use of the licensors trademarks, etc., and points the user to a separate agreement with which they must agree before being allowed to use the licensor's trademarks, etc.

In Conclusion

It is very important for software project managers to be aware of the laws that protect free software.  The current political and business environment is becoming much more volatile towards free software, and  companies, such as Microsoft, Sun Microsystems and SCO, are beginning to bring litigation against this imminent threat to their livelihoods. 

This means that project managers for free software projects are finding themselves the targets of lawsuits and mud-slinging, and though they may find this sort of environment distasteful, the author believes that a solid knowledge of the copyright laws, and the “open source” licenses that they are using to protect their software with, will help bring solace in the midst of the storm.  The author also believes that it is not only important for project managers to have this knowledge, but for end-users as well.  For the “open source” development model depends upon the end-user to submit bug fixes, or improvements to the favorite software projects, and they can only do this if they become familiar with the licenses that they are agreeing to when they participate in the free software community. 

This article has tried to address this apparent lack of knowledge by explaining the reasons behind the free software movement and the organizations that lead it, by look at some similarities that permeate all open source licenses, and then by compiling an overview of ten popular free software licenses that are used in many free software projects, as well as, listing the most important differences between these licenses.  By doing so, it is the hope of the author that project managers, information technology officers, and the general end-user will  take the time to become acquainted with the laws that protect the software that they use and implement.  It is believed that if they do, they will find that there are many limitations and restrictions inherent in free software, and their usage.  But, it is also believed that they will realize that these restrictions will lead to a better overall technology situation for all people in the future.  Not just the ones with money.  As any member of a democratic society should already know, freedom is not free... 

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*Shannon began discussing the Open Source Movement in his July Benchmarks Online article "How Does "Intellectual Property" Hamper Technology?" - Ed.