Should be easy enough to just use a javascript / ajax client to get to the Real Thing. Rewriting something text-based to use it in-browser wouldn't really net you much, if that's what you're getting at.
Why not try to write a better client for the MUDs that are still out there? Hell, at least one that I know of (
MUME) has a fairly capable XML system that can be used to write reasonable web clients. (Disclosure: I am a (retired) coder on MUME)