GNU Chess
The first version of GNU Chess was written by Stuart Cracraft. Having started in 1984 in collaboration with Richard Stallman prior to his founding of the GNU Project, GNU Chess became one of the first parts of GNU.
GNU Chess has been enhanced and expanded by dozens of programmers. Versions from 2 to 4 were written by John Stanback. Version 5 was written by Chua Kong-Sian.
In 2011, GNU Chess transitioned to version 6, which is based on Fabien Letouzey's Fruit 2.1 chess engine. Some GNU Chess enthusiasts have continued to maintain the 5.07 code base. According to CEGT version 5.60 of this code base is stronger than Fruit 2.3, the latest version of that chess engine.