> 
> One possibility is PERLmud from www.boutell.com. It looks a lot like
> tinymud, but is entirely written in perl. One could set it up as a
> series of rooms for different kinds of chat. The code has been somewhat
> hardened against hacking. 
> 
> I have it running on one of my servers.

Or anything based on the LambdaMOO server/core.  I've used that
extensively for small to large applications.

Available from ftp://lambda.moo.mud.org/pub/MOO