A xboard compatible chess and chess-variant engine
http://home.hccnet.nl/h.g.muller/CVfairy.html

Fairymax is a program that plays chess and chess variants. It uses
the xboard/winboard chess-engine protocol to communicate. Apart from
'regular' chess (also known as the Mad-Queen variant), it can play
Capablanca chess, gothic chess, knightmate, cylinder chess, berolina
chess, superchess and courier chess.