Aquarium, has been released by ChessOK (formerly known as Convekta). Version 4 Rybka 4 was released May 26, 2010. Vasik Rajlich has given the following information at the Rybka forum: Rybka 4 is a normal UCI engine, without copy protection. There are separate single-processor and multi-processor versions. Full chess analysis packages which include Rybka 4 will be made by ChessBase (www.chessbase.com) and Convekta/ChessOK (www.chessok.com). Plain Rybka 4 UCI without GUI for download only is available from RybkaChess (www.rybkachess.com). All of these versions of Rybka 4 will be identical and can be used in any UCI-compliant GUI. Remote Rybka Vasik Rajlich has now released "Remote Rybka" which is a special version of Rybka (4+ or cluster) on very powerful hardware / clusters run by Lukas Cimiotti. This can be rented for a specific period of time, though currently not less than 2 days due to overhead costs. Upon renting one has access to the Remote Rybka from one's PC, and all details of rentals are strictly private. Version 4.1 This was a version swiftly produced after the ICGA investigation was announced, to ensure no infidelities in code sourcing. It was released on March 5, 2011. Version 5 Information from the last video interview by Vasik Rajlich indicated that Rybka 5 was scheduled to arrive anywhere between the end of 2011 and the first half of 2012. As of April 2022, this never occurred. Allegations of derivative work Crafty chess engine controversy Early private Rybka engines have been accused of being a clone of Crafty, including copying specific bugs - such as comparing the result of the EvaluateMate function to a number, 99999, that it could not possibly return - and unnecessary code ("there is no earthly reason for any program that claimed to have been started in 2003 to have such code, other than that it was mindlessly copied from Crafty without the slightest understanding of its purpose"). Strelka controversy In May 2007, a new chess engine called Strelka (Russian for "arrow") appeared on the scene, claimed to be written by Yuri Osipov. Soon, there were allegations that Strelka was a clone of Rybka 1.0 beta, in the sense that it was a reverse-engineered and slightly modified version of Rybka. Several players found Strelka to yield identical analysis to Rybka in a variety of different situations, even having the same bugs and weaknesses in some cases. Osipov, however, stated repeatedly on