the open source rebuilds that were made in days are buggy and a bit broken at present.

I think it could be both. They decompiled it, likely with the help of an llm, and then vibe coded a reimplementation in rust. They claim 'clean-room reimplementation' on github, but I'm not so sure this would be considered clean room. I don't know, tho, let's wait for the lawyers and judges to say.