Decentralized forum software?

I’m a member of an active forum site that is being shut down. Members are talking anout how we might replace the forum, but it seems most roads lead to one person running a server / domain, which means we could lose the site again if that person decides he wants to shut it down again.

Trying to think of a forum that can’t go away if one person decides to walk away. In addition to chatting with others, the forum is used to host .torrent files of live concerts. It’s possible a copyright claim might threaten the new site, so something that can’t be easily killed would be appealing, too.