The Free On-line Dictionary of Computing (30 December 2018):

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.

   (2008-11-24)