Actually, it was satoshi nakamoto who (what I will say) is the founder of Bitcointalk forum since satoshi nakamoto did have SourceForge forum before Bitcointalk according to wiki (wiki article is kind of terrible by theymos)and the forum is lost but Sirius owned the domain name. Satoshi then tested Bitcointalk first which you can find a thread discussing about it before it is accessible to non-moderator forum users and sirius is the head admin until theymos became the admin running Bitcointalk effectively (see quote) Why anyone didn't mention this?. Maybe it's not the entire truth, forgot to mention it or as what theymos describes it?.
It's surprising how well-documented history can become totally forgotten... Satoshi created the forum on Nov 22, 2009, and was head administrator until almost 2011. Then Sirius was head administrator until 2012, which is when I took over.
Cobra also owns the bitcointalk.org domain name. I consider the forum to be basically owned by or at least dedicated to the Bitcoin community, though; I don't call anyone an owner of the forum.
That wiki article is kind of terrible...