GNU Chess is a chess program from the Free Software Foundation. GNU Chess can use XBoard or WinBoard as its graphical user interface.
I was not involved with the development of GNU Chess 5 or 6 and am no longer the GNU Chess FAQ maintainer.
GNU Chess 6 was first released in 2011. For information about GNU Chess 6, see the GNU Chess page on the GNU web site.
GNU Chess 5 was a completely new chess program that shared no code with versions 1-4. GNU Chess 5.00 was announced by Stuart Cracraft and Chua Kong-Sian on 10 October 1999. Here is the announcement that Stuart posted to Usenet.
I had an extremely small role in the development of GNU Chess 4. I maintained a FAQ (now outdated and no longer available), and I made sure the program remained compatible with XBoard and WinBoard.
Although GNU Chess 4 is no longer being developed, it is still of some interest to folks who like to study and compare chess engines. Here is a small collection of old versions that I've kept. The "Source code" versions can be compiled for Unix-compatible operating systems to work with XBoard, or for Windows to work with WinBoard. The "Windows ports" below use their own custom graphical interface, not WinBoard.