TinyMUX is a text-based game server in the MUSH family (which also
includes PennMUSH, TinyMUSH, and RhostMUSH). It is a platform which
allows potentially several thousand players to connect to a single
text-driven environment, interact with each other and with the
environment (which is maintain in a database). The rich programming
environment can be used to build almost anything, limited only by
your own imagination.

WWW: http://www.tinymux.org/