| Add-ons licensing are often debated and the answer to it is sadly the subjective answer to a very specific question: Would a judge see it as part of a single work or two works that operate independently and simply interacts with each other. The common understanding is that in a single static linked software the different source files are just components that makes for a single work. They are not independent. Dynamic linked software could be argued as two works but FSF has a clear opinion that a judge will see the combination as a single work and has publicly stated they will bring it to the court if challenged, and so far no one has challenged them on that view. Blender core is written in C and Blender engine is in c++. As such I would say the consensus is that all contributions to either of those must be under GPL. But you are asking about blender add-ons and those are connected via the blender API that is written in python. Python is an interpreted language so what happens here? The answer goes back to the original question, what will a judge think, and the answer is that people don't know. Some say that it changes nothing and the code parts are just as dependent as if it had been dynamically linked, in which case the add-ons need to be GPL. Other disagree, through I do not know any case law here either so it mostly just people with different view about what the judge will say. The API aspect is also an important part of the question. If the Blender API is closely connected to the internals of Blender then the distinction between an component and an independent work is blurred. Last there is two more bits I would like to add. First, just like the other comment say, GPL can not force anything to be released as GPL. Copyright law create by default a law against distribution. A copyright license like GPL is a document that describe when you have permission. The only thing that happens when someone breaks the condition of gpl is that you loose that permission. As a side effect, if you loose permission and distributed the work at the same time you can get sued under the crime of copyright infringement. The second additional bit is that interaction with non-code assets and code is itself a grey area of copyright law, but I think there is a small consensus that it would be seen by a judge as separate independent work. |