What is GPL?

GPL stands for General Public License and is sometimes referred to as GNU GPL.  GNU stands for "GNU's Not Unix" and is a computer operating system composed entirely of free software.  GNU was developed by Richard Stallman, and was provided under the GNU General Public License (GPL).  Although the GNU GPL was originally intended for the GNU operating system, it was quickly adopted by lots of other free software.  It has undergone several revisions, and there are a few "sub-types", with the latest version of GNU-GPL being version 3.

GPL and "copyleft"

GNU GPL is what has come to be known as "copyleft" - a play on the word "copyright" - and uses copyright law to remove restrictions on distributing copies and modified version of a work for others, and requiring that the same freedoms be preserved in modified versions.  The license itself may not be modified (unless you use a different name for the license,  remove the preamble and don't refer to GNU), and a copy of the GPL license must be provided along with the program in all revisions.

So, what does this actually mean?

If something is released under GNU GPL, anyone who adheres to the terms and conditions of the license may modify the work, copy, and redistribute the work or any version created from it.  They may charge a fee, or provide it free of charge - which distinguishes GPL from other licenses which prohibit commercialisation.

Some important points to consider, however:

• GPL states that a distributor may not impose further restrictions on the rights granted by the GPL - so you can't impose your own terms and conditions, contracts and so forth on top of GPL.
• GPL states that if a product is provided as a compiled binary, the source code must also be made available
• GPL states that all recipients of the product must receive a copy of the license with the program

Releasing a modified version without providing access to source codes, or using a greater license than GPL, could result in  legal cases brought by the original author.

Basically, where copyright is used to impose restrictions, GNU GPL is there to remove restrictions and ensure they stay removed with subsequent revisions.  Note that the above situations only apply when an individual is seeking to redistribute work - if you make modifications yourself and you use the modified product on your own site, then you are under no obligations to provide source code (but should still adhere to GPL and should not remove reference to the originator of the work).  If you decide to make the modified product available for others to use, then you are obligated to make the source code available.

Why is Joomla! released under the GPL license?

GPL may be just a license, but inherant with the license is a set of values that is in tune with the way in which Joomla! functions as a community based, Open Source Content Management System.  You can read more about the values and mission statement behind Joomla! at the Open Source Matters page here: http://opensourcematters.org/policies/104-mission-vision-and-values.html.

Since 1st March 2009, Joomla! started to take action to remove extensions from the Joomla Extensions Directory (JED) which did not comply with the GPL license - at the time there was widespread debate about this move, with many developers becoming embroiled in heated discussions about how this would harm their livelihoods.

See, GPL inherantly has some problems.  If you spend time, money and hard work developing an extension, and as recompense you decide to release (under GPL) the extension to the public as a commercial extension, due to GPL someone could take your source code (which you are obliged to provide), modify it to suit their needs or incorporate it into something else, and then sell it on (under GPL, which they are obliged to do).  Hence cutting you out of the equation.  They should, however, give you credit for the work which they have modified and make sure to annotate which aspects are modifications by them (so you don't get queries about their code!)

Recently there have been several instances where unscrupulous developers have done this but importantly, have not given credit to the original author for the work they had done, but have "rebranded" it as their own - effectively stealing the code and passing it off as their own work.  While GPL does not explicitly state that you must annotate what work has been modified or leave in place original headers, it does state that:

"For both users' and authors' sake, the GPL requires that modified versions be marked as changed, so that their problems will not be attributed erroneously to authors of previous versions."

Therefore, making modifications to original sources should be annotated as such, and at a bare minimum, their original sources be stated.

So, what has all the fuss been about recently?

The companies involved in "stealing" code have not been small companies, these were well known, established providers of Joomla products at the forefront of development - seemingly well respected.  They should have known better.  Some of the examples were so blatently obvious thefts of another's work that they have since altered their code to reflect its origins or pulled it completely, however other cases have not made any alterations and indeed refuse to even acknowledge the use of code from other sources.

While bad feeling is being generated very rapidly towards the organisations involved through various social media channels, it is important that people take the time to actually read and attempt to understand the GPL license to avoid inadvertantly ending up on the wrong side of the license.  I'll freely admit that before all this kicked off I had a very sketchy understanding of GPL, and thought I knew what it was all about (after all, I've been using Joomla! for several years now!) however I hadn't ever taken the time to actually read the GPL!

So, if you do one thing today, take the time to head over to http://www.gnu.org/copyleft/gpl.html and read the license - some of it might be a bit legal-speak but the majority is plain english, and hopefully it'll help inform people on an important aspect of our community.

Sources:

http://www.gnu.org/copyleft/gpl.html

http://en.wikipedia.org/wiki/Copyleft

http://en.wikipedia.org/wiki/GNU_General_Public_License

http://community.joomla.org/blogs/leadership/636-jed-to-be-gpl-only-by-july-2009.html

http://opensourcematters.org/policies/104-mission-vision-and-values.html