For example, I’ve GPL software. I’m the author of this GPL software. This GPL software has, between its code, Doxygen comments. These Doxygen comments are written to generate a CC-BY-SA html page, in order to upload this generated documentation in my project website under CC-BY-SA license.
But, is the Doxygen documentation output a “derivate work”? After all, this documentation is based on my GPL source code. In this case, the documentation must be GPL. But, I want the documentation is CC-BY-SA, because it is documentation. GFDL doesn’t help. GPL code can’t become GFDL (the opposite yes).
If this output is really a derivate work, I think, creates a strange situation, because, if I distribute my work, recipient users can’t legally distribute the generated documentation: while with my work I can do I want, the users don’t, thus, they have to distribute any derivated work with the same license I offer them.
What is the solution?
1
This is really a tricky question (of the ask-your-lawyer kind).
Since you are the author of the software, you can make your intentions clear and avoid any ambiguities by adding a “Doxygen-comments are CC-BY-SA” exception to your license, along the lines of:
Additional permission under GNU GPL version 3 section 7
In addition, as a special exception, the copyright holders of [name of your program]
give you permission to distribute the Doxygen comments in this source and any work
derived from those comments ("the documentation") under the CC-BY-SA license.
5
To be a “derivative work”, something must first be a work. Under United State law, only a creative process can create a work. An automated process cannot create a derivative work because it cannot create a work that didn’t exist before. (Other than a few specific exceptions created by statute.)
If you think about it, it can’t be a derivative work. Say you run program A on text B and produce work C. If this is a new derivative work, who holds copyright on it? No human being created it, and a program can’t hold copyright.
Non-creative combinations can’t create any new work, derivative or not. What mechanical processes can create is an aggregate work. It’s legally the same as if I glued two DVDs together (or combined two files on the same storage medium). There’s no derivative work, but the two DVDs stapled together are an aggregate of both works.
See 17 USC 103(b): “The copyright in a compilation or derivative work extends only to the material contributed by the author of such work, as distinguished from the preexisting material employed in the work, and does not imply any exclusive right in the preexisting material.”
Also see circular 14.
Who would the author of the derivative work be?
19
There is nothing stopping you from applying different licenses to the same code. If I understand you correctly, you have code written and controlled by you that has comments you want to release under a CC license and code you want to release under GPL. So just do that. The comments will be released under the GPL and under the CC license, so if people use the comments according to the CC license, they’re fine.
The GNU GPL FAQ talks about automatically generated code specifically, so it might answer your question if I misunderstood. (It also covers a lot of other corner cases.)
3
The question is moot.
If you are the author of the program, you have all the rights to distribute it under the terms you like. So if you generate the documentation under a different license, you will have it under a different license. Because you said so.
The program wasn’t written by you? Then, the documentation you produce should be GPL, but that presents a different problem. The GPL doesn’t talk about documentation. It talks about software.
So if you want to reprint commercially the output of a doxygen run of a GPL program you did not write, here’s what you do: you write to the author and ask for explicit permission. Same thing if you want to distribute those docs under CC-BY-SA. You don’t stick the label, you ask the author to stick it.
Law isn’t a weird mind game. It’s about people convincing juries or judges. Judges hate mind games and juries sometimes don’t even get the law correctly. (§ Apple vs. Samsung)
So, worst case scenario.
The author is deceased, the heirs are stupid and they just like to sue people. You reprinted commercially the output of a doxygen run of a GPL program. My guess is (but IANAL) you still may win, but it might be harder than planned and you may face a judge very tedious on distinguishing software from written word meant for human consumption. I’d still bet on a 70% success rate.
Why did I say reprint commercially? Cause it’s hard to sue people for damages if you can’t tell the value of the “work of art” (the documentation) that’s been illegally distributed. If the subject of the suit is unsellable or of unquantifiable value, you cannot claim enough damages to pay a lawyer.