No, not that type of mud! MUD - Multi-User Dungeon. It's a type of text game like those popular before computer graphics became descent. They are multi-player games that share some similarities, yet each one is unique. MUDs are coded by volunteers called "wizards." Noone gets paid for it. The only fee is internet access.
I code for a MUD called Dead Of Night where I go by the name of Phi. Check out the bard and mage classes... they are my work. Also check out the Deadtimes, a quarterly newsletter about Dead Of Night.