The GPL is viral. How does this apply to the LaTeX eco system if one uses a package licensed under the GPL2++?

  1. If I use it in a document, must the document also be licensed under the GPL?
  2. If I use it in a package, must that package also be licensed under the GPL?
  3. If I use it in a document class, must the document class also be licensed under the GPL?
  4. If I create a program that creates LaTeX code which uses 1, 2 or 3 - must that program also be licensed under the GPL?
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    @Martin I assume that the background to the question here is that TeX code is used 'raw' by TeX (ultimately \input), with no compilation. There's a contrast to a compiled GPL program, where I can use it's 'defined interfaces' without accessing the code and without needing to license under the GPL. My worry from the POV of TeX-sx is that this is a legal question, which is not the area of expertise of the majority of us (and indeed the network as a whole avoids legal questions for I think obvious reasons). – Joseph Wright Aug 27 '12 at 13:48
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    This question is misleading: The GPL is not independent from the national law. The answer differs probably a lot between different countries. Your question can not be answered »for the whole world«. However, the question is short, but a solid answer even for one country requires a lawyer who is familiar with copyright law, e.g. of your country (Germany) and GPL. So this is not the right place to ask this question. I'm not aware that such folks are reading questions here. That said: To what end are you asking this question? TeX and LaTeX have been around for decades and nobody ever doubted th – Keks Dose Aug 27 '12 at 14:33
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    @MartinSchröder The document you produce is not a program, but data. You aren't required to release under the GPL images produced with "The Gimp". – egreg Aug 27 '12 at 15:27
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    @MartinSchröder gnu.org/licenses/gpl-faq.html#WhatCaseIsOutputGPL – egreg Aug 27 '12 at 19:33
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    @AndrewStacey: Then it should have been closed as OT, not as NARQ. And I'm not sarcastic. :-) – Martin Schröder Aug 28 '12 at 18:53

My current understanding of this is: All cases must be licensed under the GPL, as they are all modified versions, not aggregates. Or the LaTeX package is a library.

Which is why the GPL is IMHO the wrong FSF license for LaTeX packages; the LGPL would be much better.

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    Many people who make a contribution want to make it Free. GPL is what they know, what they have heard of, what they admire. I suspect that you are after an education issue (whether I agree with you or not :-) ). – Jim Hefferon Aug 27 '12 at 23:33

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