GNU Go is free program that plays the ancient board game of Go. Its original concept is based on the article "Programming the Game of Go", Byte, Vol.6 No.4, by J. K. Millen. GNU Go has since evolved into a more sophisticated program. After thousands of games played on the No Name Go Server (NNGS), it is rated around the 8th kyu level.
The NNGS (No Name Go Server) is a full-featured server which allows you to play the game of Go over the Internet. It runs on Unix machines as well as on Windows, and supports connections from many clients (both graphical and text based). The code is based on the Free Internet Chess Server (FICS) code, and currently only supports the game of Go.
It works under Cygwin as well. Just install Cygwin, add the X11 packages (and X11 development libraries!), and compile.
If you get an error about a missing X11 library after running 'make', use the following compile line. It adds the X11R6 lib path to the compile line used in the Makefile.
c++ -Wall -Wno-return-type -O2 -o seahaven main.o util.o card.o stack.o score.o auto.o -lX11 -lXext -lm -L/usr/X11R6/lib