The documentation text is under those licenses as they’re part of the code. Since they’re permissive licenses, you can take them and transform them into something which is NOT automatically licensed the same, you can make it proprietary. However, automatically processing it with software is certainly NOT a creative process, so I think the result is free as well. Anyone can replicate the process and create the same documentation themselves, there’s nothing creative you add in the process, EXCEPT maybe the Doxyfile, i.e. the configuration. This I think is the borderline case and depends on how much original work you’ve added – if you’ve changed two lines in the Doxyfile, there’s nothing to talk about (in the same way you can’t demand copyright for a three word text). But if you build your own color palettes and include some long texts, that could be seen as a work protected by copyright, which you would have to explicitly license again.
By that argument, compiling code isn’t a creative process because anyone with a correctly configured compiler can compile source code (“process the source with software”).
Surely the same logic applied to compilation should apply here?
The author manually creates the documentation comments, therefore it is a creative process and the HTML generation step is merely a way of reformatting the already human-created information, in the same way that compiling is merely a way of reformatting source code.
Sure, compilation is the same thing, no extra creative work emerges there. E.g. if you take an MIT licensed code and compile that, you don’t get copyright for the binary, meaning anyone else can create the same binary and do whatever they wish with it.
Yes, it is a non-creative step applied to creative work – so no extra rights come to existence, but the rights that already exist still apply.
Just F.Y.I. in the Doxygen license section of the Doxygen documentation’s home page (Doxygen itself is GPL licensed) they state:
Documents produced by doxygen are derivative works derived from the input used in their production; they are not affected by this license.
@MLXXXp it seems the purpose of that statement is to make it clear that the GPL doesn’t apply, which is logical here. I though the term derivative work was wrong here, but actually I may have had a wrong understanding of what that term meant – that can happen, IANAL. From Wikipedia:
A derivative work is an expressive creation that includes major copyright-protected elements of an original, previously created first work (the underlying work).
So this fits the documentation – it is an expressive work (the comments it contains make it such) derived from some other expressive work (the source code). The deriving process doesn’t have to be an expressive work though, which is where I’ve misunderstood the term. In other words, it is an expressive work and it is different from the original, but there may have been no extra expressive work to create extra rights.
So yeah, everything seems to fit.
Yes. I should have stated that I was quoting the document to point out that the Doxygen organisation considers the output to be a derivative work. As you say, not inheriting the Doxygen licence makes sense.