The GPL is itself essentially a proprietary software license! Specifically, the WordPress founder made the decision to adopt the GPL offered as a model by the Free Software Foundation. They had the complete freedom to choose any type of license - including options that were commercial and restrictive on redistribution rights - for WP itself.
WP chose the GPL because of their commitment to open source software. It fits with their philosophy on how software should be shared and distributed. This is, of course, very valuable to the software world and perfectly acceptable for them to do so.
However, what it does NOT do is give them the right to arbitrarily impose the GPL on 3rd party, private developers.
WP as a private organization does not have the legal right to impose the GPL on another 3rd party developer just because that developer releases an application of any variety that works with WP (even with deep integration). An application does NOT have to be limited to strict interaction though a formal API (as suggested by Mark Jaquith in his excellent analysis) to avoid the gravitation force of the GPL.
The GPL is also NOT triggered by wholesale copying of every line of WordPress code, until such time as it is distributed by the 3rd party dev with a non-GPL license.
There are two important criteria for GPL applicability:
When both of these criteria are met, the GPL is triggered, and the 3rd party is subject to fulfilling all terms and restrictions imposed by the GPL.
Drew Blas demonstrated that Thesis does include several snippets of WordPress code. And, of course, Chris Pearson (DIYThemes) is distributing Thesis under a non-GPL, restrictive commercial license.
So did he trigger the GPL and is he currently violating it? The question is now entirely dependent on one primary consideration:
If it is considered “fair use”, Pearson/Thesis does NOT infringe on copyright, does NOT trigger the GPL, and is therefore completely within his rights as a 3rd party developer to continue distributing the code under ANY license of his choosing.
The problem with the “fair use” analysis is that it is also very difficult to determine the answer, and there does not seem to be prior case law that fits this particular situation accurately. Had Chris copied code to produce a “clone” application, it would almost certainly be classified as a copyright infringement (not fair use).
The question of fair use will have to determine if there is substantial similarity between Thesis and WordPress itself, or code snippets thereof. If there is found to be substantial similarity (which is likely the case here), it will weight the question of whether or not that code has limitations on its exclusive rights by examining the four criteria of the fair use doctrine.
In any future lawsuit between Mullenweg (WP) and Pearson (Thesis), this is likely to be the primariy question the courts must determine. Until that determination is made, the GPL should not even be a consideration as WP has no specific rights to arbitrarily impose its license on any 3rd party developers UNTIL such time as those developers are violating WP’s fundamental copyrights.
Let’s hypothetically assume that a lawsuit proceeds and the court determines that Thesis has violated the copyright of WP outside of the criteria of “fair use” and is infringing. Is there any way that Pearson can adapt his Thesis offering to eliminate the components that are violating copyright and triggering the GPL?
Yes. Mark Jaquith made reference to exactly such a scenario is his analysis. He referenced a split license. He was discussing it in the context of allowing non-GPL protection for JS, CSS, and image files.
However, a split licensing scenario can also be used by Pearson to avoid copyright infringement (if that is the case) and to avoid being held subject to the GPL.
In the case of Thesis, the split license would be for:
The adapter would include the portion of code required for deep integration with WordPress. As we know, without this interfacing code, Thesis cannot run independently. This code provides the hooks into the WordPress framework that Thesis needs to work.
Since the adapter code may include WordPress snippets not protected by fair use, it would have to be released under the GPL license. However, the rest of the Thesis code base would then be free from any WP code infringing copyright, and could be licensed under a proprietary commercial license with any restrictions of Pearson’s choosing included.
Therefore, any 3rd party developer can develop an add-on or extension of a GPL licensed framework and not be subject to it, provided they release any deep integration code in a separate adapter package also licensed under the GPL as a part of a split license package.
GPL will remain 2nd in Command. General copyright law is the first application. Until (a) copyright is infringed, (b) the 3rd party code is distributed, and (c) the 3rd party is not licensed under the GPL, only fundamental copyright can be applied.
If the 3rd party developer used a split license, and packaged all copied code snippets from the GPL source application into a GPL-licensed adapter package, they will also gain exemption from imposing the GPL on the rest of their application licensing.
Copyright is King here. The GPL is a Prince at best. Yet, Chris Pearson’s Thesis code base DOES include code snippets from WordPress.
Unless, he can demonstrate fair use, or revert to the split license/adapter strategy, he may find that he is, in fact, required to release Thesis (as it is now) as GPL only. This remains to be seen and is certainly not an easy determination to make.
There is no debating the FSF’s current interpretation of the GPL, and their stated intention. Mark Jaquith also pointed out that Drupal and Joomla have stated the same position.
The first problem with this is that their “intention” may be taken into consideration, but it is the actual legal text of the GPL that is the standard to which all questions related to the GPL must be evaluated.
Secondly, because nobody can arbitrarily impose a private license on 3rd party developers, their interpretation or intentions will NOT matter until such time as the GPL is triggered.
Until general copyright infringement, outside of fair use, is proven, that won’t happen.