I was never involved in running a multi-line BBS (so, no BBS-based MUDs for me), but I did help with a couple of boards that ran a Turbo Pascal-based single user MUD-like game (called "Cyberspace"). It was TinyMUD-esque. At one point we had 10 - 12 people actively building rooms, adding mobile NPCs, etc. It was loads of fun even though only one person at a time was interacting with the software.