The 'gnuchess' program deals with chess quite well. It can compute legal moves, perform rough evaluation of game states, and actually play chess. This library is meant to interface with gnuchess to provide (at the time of writing) basic chess functionality, with an eye towards computing legal moves.
Because this library is intended to interface with 'gnuchess', it requires that the gnuchess program be installed.
This library is distributed as a Ruby Gem. I recommend using rubygems to install it, as this should be quite easy.
See the documentation for module RGnuchess.
This software was originally written by Leon Barrett ([email protected]) in the spring of 2005.
This software is published under the Gnu General Public License. Maybe it should be under the LGPL, but let's face it: if you're worried about that, you can afford to recreate this functionality. See the LICENSE file for the license text.