Gnuchess

GnuChessMac is a free Macintosh chess game derived from GNU Chess, distributed under the GNU Public License. The 4.0 lineage was ported by Dan Oetting with Tom Gerardy and Erich Oetting, building on the version 3.0 Mac port originally done by Airy Andre, with later 4.0 work by Rolf Exner.

Engine heritage

The Mac port starts from the cross-platform GNU Chess 4.0 engine, with substantial changes to the search routines, opening book, and transposition table to suit the Macintosh environment.

Mac interface

The user interface descends from Airy Andre's earlier 3.0 Mac port, providing a native Classic Mac front end over the imported engine, with window sizes, positions, and command keys tuned over successive releases.

Save, restore, and undo

The 4.0b5 release added the ability to save and restore games in progress and an Undo command for players who change their minds mid-game, addressing two of the most frequently requested features.

Apple Event chess engine

Rolf Exner's 4.0 release adds Apple Event support, standard algebraic move notation, and lets GnuChessMac act as a chess engine for other programs such as ExaChess and ExaChess Lite.