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I am about to release a new document class I developed myself. I am currently in disarray about what license can/should be used for such a project.

The "default" license used for LaTeX code seems to be the LPPL version 1.3c, but it only cares about file names used in derivative works and maintenance succession of the original work. But I would like to use some kind of copyleft license, which imposes the right to redistribute modified versions of the document class, to reuse code of these modified versions in other projects and to backport these changes into an original project. But I don't want to use a license which would require to mention and redistribute this document class (or a link to it) with every PDF produced with it because it would be ridiculous.

I have read the discussion about implications of the classicthesis being licensed with GPL, as well as an answer and comments to this question and the detailed history of the controversy regarding LaTeX code licensing (Reflections on the history of the LATEX Project Public License (LPPL) — A software license for LATEX and more). What I have understood so far is:

  1. There are different opinions about whether an article (its source code and/or produced PDF) typesetted using a document class licensed under GPL must be also under GPL. It seems like the FAQ answer "In what cases is the output of a GPL program covered by the GPL too?" on the gnu.org suggests that it is, but I am not sure.
  2. It seems like the LGPL license if used for a document class would still require a mention of usage of this document class in each produced PDF, which would be ridiculous.
  3. The LPPL license seems to be the only appropriate license for my case, but it is not enough for me.

The question: Is there a ready-to-use set of extending clauses for the LPPL which would make it a copyleft license? Or is it a terra incognita and consequences of trying to extend it this way are yet unknown?

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I would recommend to use the GPL license with an additional permission for creating documents based on the document class/stylesheet.

You could for example use this as additional permission:

As additional permission under clause 7 of the GPLv3 license, you are allowed to create documents that use this document class or stylesheet as-is without following all requirements of the GPL license. Such a document can be published under any license of the author's choice.

This makes it clear that you don't intend to extend the copyleft provisions to documents using the document class, without removing them for other cases.

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    And what about linking with LPPL licensed packages, which are already used? The FAQ answer "What legal issues come up if I use GPL-incompatible libraries with GPL software?", suggests to enumerate libraries I allow to link with. Can I just allow to link with anything under LPPL? Also, GPL contradicts enforcing usage of different filenames for modifications (like in LPPL). I would like to also have this restriction, but I am ready to forsake it if it is essentially incompatible with any kind of copyleft. Aug 2, 2023 at 18:53
  • @MykhailoMishchenko, for linking with LPPL packages, you would also need to include an additional permission to the GPL license. You can write that to allow linking with anything under LPPL, but it would only be needed for packages you refer to directly. Required renaming cannot be added to the GPL, but is in itself not incompatible with a copyleft license. Aug 3, 2023 at 6:14
  • The phrase "without following all requirements of the GPL license" seems like it's not what's really intended. Also, "as-is" is a bit problematic. Does the word "as-is" mean "as-is, without modifications", i.e. so that if I modify the document class, then the Additional Permission no longer applies to the PDFs I produce from that modified class? I.e. then that resulting PDF needs to be delivered with full source as well?
    – Brandin
    Aug 3, 2023 at 7:10
  • Instead of GPL + exception, why not instead do LPPL + exception? LPPL does not mention the procedure for adding an exception (to say that the LPPL terms do not apply to compiled versions of the documents, such as PDFs). As copyright holder you may always add an exception. Also it might be good to also allow downstream users of your class to delete this exception from their version if they wish, in order to maintain LPPL compatibility. This is what the GPL classpath exception does, for example: gnu.org/software/classpath/license.html
    – Brandin
    Aug 3, 2023 at 7:52
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    And so yes technically you're right, the "GPL v2 + Classpath" is indeed (technically) another separate license (separate from "vanilla GPL v2"). I think that's why the drafters of the Classpath exception wrote that you're allowed to remove the it from your version if you wish. I.e. it allows you to "Downgrade" back to vanilla GPL v2 if you wish. Linux, on the other hand, doesn't allow removing the syscall exception text. But if we want to remain on the same technicality, then technically GPL v3 + some custom exception still seems like technically a different license than vanilla GPL v3.
    – Brandin
    Aug 3, 2023 at 9:07

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