You’re referring to a different kind of dispute than I (and parent) was talking about. In this case, Stallman did handle the dispute about whether GNU Parallel’s citation notice conflicted with the terms of the GPL.
Okay that makes sense. You're saying that since the GPL itself is not open, that it needs Stallman's approval for modifications that are not explicitly allowed. And I was saying that it does not necessarily mean those modifications are enforceable between two parties in a random jurisdiction, which comes down to courts and whatnot.
Yes kind-of… in this case Parallel’s notice is not a modification of the license at all, and Stallman is the person who ruled on this question and confirmed this to be true. The GPL doesn’t prevent authors from including a notice, and having a notice doesn’t conflict with the terms of the GPL.
I feel like the whole problem here is that the legality of Parallel’s notice, and the separation of the notice from the GPL, is not at all clear. The language is confusing to users. People who take the license seriously are staying away from Parallel because of the fear of accidentally breaking the license terms.
That’s not true. The language of Parallel’s citation notice, while confusing to some users, does not impose any legal requirements and is not part of the license. Neither the notice nor the license claim otherwise. RMS, and more importantly, Ole Tange, agree that Parallel’s notice is not legally binding, and intended to write it that way, and there is a publicly visible history of this intention and agreement.
RMS, not being a judge, is incapable of "authoritatively" or otherwise determining whether this notice is legally binding.
If it is something that needs to be "confirmed" by someone "authoritatively" then you should ask a lawyer for advice. You should not ask a programmer for a "ruling".
What RMS might be saying is "we won't seek to enforce it". That is completely different.