alt Hacker NewsThey're essentially saying "yes, the code is open source, but you're not allowed to modify it or we'll ban you and threaten you with legal action", which is completely antithetical to the whole idea behind open source (especially the GPL which literally says in the license text itself that it was created to protect your right to run modified software). "Violation of the open source social contract" is a good way to describe it.
You're correct of course that this is an entirely distinct argument from what Bambu's legally allowed to do under existing law.
You can run modified software per the GPL but that does not include the right to connect to Bambu's servers with your modified software. That is entirely reasonable (especially since this is not some social/messaging application). If I release a client as open source, that doesn't mean it's OK for modified clients to connect to my server. I expect you to use it offline or set up your own server to connect to.
I don't know if that is what is happening here because the article is talking about a fork that is bypassing Bambu's servers entirely (which is permitted under the AGPL) and Bambu is not happy.
Edit: On re-reading, it seems to me the fork is still calling Bambu's servers. It's just bypassing some things.