AberMUD
The first popular open source MUD. The first version of AberMUD, named after Aberystwyth, UK, was written in B by Alan Cox, Richard Acott, Jim Finnis, and Leon Thrane, at University of Wales, Aberystwyth for an old Honeywell mainframe and opened in 1987. The gameplay was heavily influenced by MUD1, written by Roy Trubshaw and Richard Bartle, which Alan Cox had played at the University of Essex. In late 1988, Alan Cox ported AberMUD to C so it could run under UNIX on Southampton University's Maths machines. This version was named AberMUD2. Various other versions followed.