So, technically, he can't actually add restrictions to the license after he's license them, and if these are taken to not be part of the license, you'd be safe to just follow the license as usual.
But if this informal text is taken to reflect the intent of the parties, then it might kind of reflect on how the license is meant to be followed, which isn't great. It's not only inconsistent with the spirit of the GPL, but also the language, as it talks about "use," seems to require a direct link to "the recent version..." A lot of companies have been offering alternative interpretations of the GPL, and theoretically if those interpretations are taken as evidence of the intent of the parties, they might affect the contract. Or they might be seen as parol evidence, IE not relevant to the contract, but it's hard to say. So I wouldn't advise risking it...
But the text is informal and the party seems to not really understand the license to begin with (again, he's talking about "use," that's not really even relevant to copyright law), so he might not really mean anything by it. I would not assume ill intent. It might be worthwhile to informally reach out to this community and help develop language that just clarifies what the GPL already says, instead of conflicting with it. The community might appreciate that. Worst case, they get angry and defensive, and attempt to move to a different (presumably proprietary) license, in which case, you learned the easy way that they don't play nice. Don't learn the hard way.
Daniel J. Hakimi
B.S. Philosophy, RPI 2012
B.S. Computer Science, RPI 2012
J.D. Cardozo Law 2015