Maybe that was their game with the federation stuff. "Hey we didn't start this, we were just following suit on this open source project". Anyway this logic wouldn't fly in any court, they can't have a copyright on text-based social media. They can only own their branding. Musk is just throwing a hissy fit again
I think Elon is trying to say they're stealing IP because lots of the Twitter employees he fired went to work on Threads. This is probably where the fediverse stuff comes in clutch, as they're just implementing ActivityPub, so it's not like it's industry secrets or anything.
Yeah, people have suggested they believe Meta would/did use Twitter code. I don't know why they would... Meta already has IG, which is set up almost exactly like Twitter, and if anything they could imitate code from Mastodon.