This is a Sugar front end to the gnuchess program. More details on
gnuchess can be found at:

http://www.gnu.org/software/chess/

and

http://www.gnu.org/software/chess/manual/

Some of the artwork comes from the Gcompris chess program. Other
artwork was inspired in part by:

http://lovesexandthermonuclearwar.wordpress.com/2012/04/04/assorted-chess-tools/