The tight-knit world of chess has been hit by an extraordinary scandal that has seen the creator of the program that won the last four World Computer Chess Championships (WCCC) stripped of his titles for allegedly plagiarising rival software.

The International Computer Games Association (ICGA), which organises the WCCC, said it had believed that programmer and MIT graduate Vasik Rajlich had copied two open source chess engines, Fruit and Crafty, in creating his hugely-successful Rybka chess-playing system.

This violated rule 2 of the tournament rules, that all programs must be the work of each developer, unless clearly stated, the ICGA said.

The executive committee voted 5-0 to disqualify Rajlich from the last four world championships, all of which were won by Rybka, and his one second placing in 2006. Every program that finished behind Rybka will now move up on place, elevating four rival programs to champion status.

Exactly how the ICGA came to its conclusion is contentious. Rybka is a commercial system that does not publish its source code so the governing body reportedly reached its conclusions using reverse engineering analysis of apparent similarities between the chess program and its counterparts.

According to a public analysis, the formulas within Rybka were claimed to be identical in numerous respects, particularly to the Fruit program.

Critics will point out that Rajlich’s program still won four World Computer Chess Championships which suggests that it must have had some extra advantage beyond mere copying of rivals. Others will sympathise with Rajlich’s difficulty in ever defending his creation without releasing its source code for a line-by-line comparison.

Earlier this year, respected chess expert and ICGA president David Levy has published an article, Attack of the Clones, on the theme of chess engine cloning which mentions the allegations against Rajlich and Rybka.

Traditional chess is the pitting of one mind against one another but increasingly as computing power has risen in the last two decades that conflict has become a proxy war of chess engines, programs that combine the combined knowledge of many minds with huge calculating power.

The most famous (or infamous depending on your perspective) example of a chess-playing computer gaining public attention was ‘best chess player in the world’ Gary Kasparov’s 1997 2-1 series defeat to IBM’s Big Blue supercomputer, later the subject of a book analysing the event by the machine’s co-creator, Feng-Hsiung Hsu.

Kasparov was said never to have recovered from the defeat. As then IBM head Lou Gerstner said at the event press conference. “I just think we should look at this as a match between the world’s greatest chess player and [pause]…Garry Kasparov.”