You know what's interesting here, nobody mentioning MajorMUD. That was (and somewhat still is) the kinda-not-a-door-game door game serving as the engine of a lot of BBS use. Unfortunately, MetroBBS (the company that owns the IP) is still holding out for some kind of MMO or movie deal or something and the pricing for this game is silly. Also, being from the KC area, I have it on very good authority that some of the source code for MM was lost during an office move. And this is why (in addition to having lost their main programmer) there haven't been substantial updates in years.