I tried to go there last night and it looked a bit different than a year or so ago. Is there a new feature? I could see myself there as "guest" (I was the only person in there, of course) but it had another step before I was actually in the chatroom.
It pops up asking you to authenticate. If you don't want to use Twitter or Facebook for authentication, you choose "Guest" and then type a user name. I think we always had to type in something but it's been a long time since I'd been in there too.