[Bjartr]

The message isn't part of the license, and it's phrased in a way that wouldn't be binding if it were.

It says "please cite" and "feel free to not cite if you pay".

It doesn't say "must cite" or "you may only not cite if you pay".

IANAL, but it doesn't seem like it would interact with the GPL at all. So the worst that could be said is that the implementation is annoying or in poor taste.

[paulmd]

Software cannot be distributed with a clickwrap agreement under the GPL. Requiring the user to affirmatively agree to a contract is a clickwrap agreement even if the terms are non-monetary. The old “you are making a second agreement, not the one the software is distributed under” approach.

Notionally the GPL allows you to disregard this but it may or may not be binding depending on your jurisdiction, and it’s certainly distasteful and against the absolute spirit and most likely the text of the GPL. This is an incompatible term being forced on the end user and the entire license might well be void.

[aidenn0]

It's not a clickwrap agreement, since the user doesn't agree to anything:

   To silence this citation notice: run 'parallel --citation' once.

[paulmd]

did you ignore all the stuff before that about the implication of using that option and what the user agrees to by using it?

this is like saying that a user doesn't actually agree to anything just because they clicked "accept" in a EULA. you're just clicking buttons in software, it doesn't obligate you to anything!!! but actually yes that is most likely fairly binding in a lot of jurisdictions.

that is, again, literally the definition of a clickwrap licensing agreement and you cannot do that in GPL software, even if it's non-monetary. Requiring the user to submit a selfie in a funny hat would not be permissible under the GPL either. You can't limit what the user does with the software and how, or else it's not GPL.

it's open and shut, clickwrap agreements completely subvert and nullifies the moral stand the FSF is trying to make. And it doesn't matter how innocuous it seems, it undermines the whole point of the exercise.

fortunately the GPL includes a "severability" clause that basically allows you to ignore this and grants you a license regardless. but it is not a good look, it is not good behavior, and if every GPL'd package started adding random clickwrap agreements with big "IM A DOODOO HEAD IF I IGNORE THIS" parameters the whole ecosystem would degrade.

Arch and others are not only allowed but actually morally and practically in the right for stripping these messages, and it doesn't reflect well on Ole at all that he then goes on and throws more tantrums because he doesn't like the consequence of the license he chose.

If he wants to go proprietary, or BSD (which requires acknowledgement!), that's fine, but he's being a child and the terms he are adding are utterly uncompliant with GPL, and it's unprofessional for FSF to even humor him on this. If there were a hundred Oles the FSF would have a real problem on its hands, it's only because he's N=1 jerk that this is remotely tolerable.

[aidenn0]

It doesn't look like it obligates me to do anything. It contains a request to cite, not a requirement:

  If you use programs that use GNU Parallel to process data for an article in a
  scientific publication, please cite:
  
    Tange, O. (2023, July 22). GNU Parallel 20230722 ('Приго́жин').
    Zenodo. https://doi.org/10.5281/zenodo.8175685
  
  This helps funding further development; AND IT WON'T COST YOU A CENT.
  If you pay 10000 EUR you should feel free to use GNU Parallel without citing.
  
  More about funding GNU Parallel and the citation notice:
  https://www.gnu.org/software/parallel/parallel_design.html#citation-notice
  
  To silence this citation notice: run 'parallel --citation' once.

[edit]

This is really similar to the kerfuffle where the maintainer of Home Assistant asked distros to not repackage HA; it's a request, a bit at odds with community norms for libre software, but one that people are legally free to ignore.