International Computer Games Association (ICGA) has found that the dominant computer chess program and engine in the last half of the noughties, Rybka, programmed by Vasik Rajlich, has broken its rules by incorporating elements of older programs, especially Crafty and Fruit without attribution. They have stripped Rybka of World Computer Chess Championship titles earned 2007-10. Rybka has recently been supplanted as the top engine by, amongst others, Houdini.
However this issue of using elements of other programs is not limited to Rybka alone. Should new programs have to reinvent the wheel
or be able to build on well understood elements of the past? If so, what are these elements? I’m not clear on this.
Also in an era of free engines and their heavy use by players there may be commercial implications for the future.
You can read the most recent in a series of articles by ChessVibes on this issue.

Source: The Week in Chess