WChessV is a free computer program designed to play many chess variants. ChessV is an open-source, universal chess variant program with a graphical user-interface, sophisticated AI, support for opening books and other features of traditional chess programs. The developer of this program, Gregory Strong, has been adding more variants with each release of ChessV. Over 100 chess variants are supported, including the developer's few own variants and other exotic variants, and can be programmed to play additional variants. ChessV is designed to be able to play any game that is reasonably similar to chess. ChessV is one of only a few such programs that exist. The source code of this program is freely available for download as well as the executable program.
WFairy-Max is a free and open source chess engine which can play orthodox chess as well as chess variants. Among its features is the ability of users to define and use their own custom variant chess pieces for use in games.
WGNOME Chess is a graphical front-end featuring a 2D and a 3D chessboard interface. GNOME Chess does not include a chess engine of its own, so to play against the computer a third party chess engine must be present. Most Linux distributions package GNU Chess as the default chess engine with it. Additionally GNOME Chess supports third party chess engines, with known ones automatically detected.
WGNU Chess is a free software chess engine which plays a full game of chess against a human being or other computer program. The goal of GNU Chess is to serve as a basis for research. It has been used in numerous research contexts.
WPyChess is a free software chess client developed for GNU. It allows users to play offline or online via the Free Internet Chess Server (FICS). PyChess also incorporates a built-in chess engine, which in contrast to most other chess AIs is written in the Python language and focuses more on fun of play than raw strength. For more advanced users, PyChess allows for virtually any other external chess engine to be used with it.
WShane's Chess Information Database (Scid) is a free and open source UNIX, Windows, Linux, and Mac application for viewing and maintaining large databases of chess games. It has features comparable to popular commercial chess software. Scid is written in Tcl/Tk and C++.
WXBoard is a graphical user interface chessboard for chess engines under the X Window System. It is developed and maintained as free software by the GNU project. WinBoard is a port of XBoard to run natively on Microsoft Windows.