Derivatives
Although Fabien Letouzey's development of Fruit stopped in 2007 with version 2.3.1, the earlier open source 2.1 version provided the basis for many other programs.
Toga II is a derivative created by Thomas Gaksch. It has more chess knowledge, multi-processor support, and perhaps a better search algorithm. It is based on Fruit 2.1 and is free. The strongest versions are 1.4 beta5c and 1.4.1SE. Experimental versions of Toga II running on computer clusters have competed in the World Computer Chess Championship (WCCC).
In 2008, forks of Toga II started to appear, like Grapefruit and Cyclone.
GambitFruit is another free derivative of Fruit 2.1, created by Ryan Benitez. It plays a more aggressive style and has more chess knowledge. GambitFruit also incorporates improvements from Toga II. Development of GambitFruit stopped in 2005.
In June 2011, the strong chess engine Rybka was disqualified from the WCCC, after a lengthy investigation found evidence of plagiarism of Fruit and Crafty. The author of Rybka has since declined to comment.
An up-to-date ranking of Toga II and Fruit derivatives is found at the CCRL.
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