Ok, but the catch being that, if something is registered in Public Domain, nobody can claim ownership of it - that's kinda the point of the public domain. They can, perhaps, claim ownership of the performance of said piece, but not the piece itself. There's always a loophole.

And, if I'm being honest, if Squenix is claiming ownership of everything that is done via the Perform emote...why the flying, fuzzy <explative deleted> would anyone use it?