I don't know of any decent MUD servers for Amiga I'm afraid. I saw one once that had potential, but I don't remember what it was called and I do remember that when I looked into it, it made me shudder with dread at the idea of (necessary) customizations.
I'd strongly advise against running a MUD on your personal machine though - they tend to be pretty intensive on the system - especially if you've got a reasonably large world with lots of wandering mobs.
If you really want to do one on the Amiga, you've got three options:
1 - write one from scratch and hook it into a telnet server
2 - write one from scratch including it's own transport
3 - port one from somewhere else. If you go this route, I may be willing to help with porting one of the Diku family since that's my preferred MUD system.
Regards,
Ben de Waal.