Isn't there something slightly ironic about accusing the best pupil in the class of peeking over the shoulders of the other students during tests? Not that it can't be a correct accusation, but if this guy "cruised to victory in four consecutive WCCC tournaments in 2007, 2008, 2009 and 2010" then he must have done something right (other than copy-paste).
From a copyright perspective I can certainly see an issue, but that would be between Rajlich and the author of this Fruit I would say.
Actually, the argument isn't about cut&paste programming. That would be somewhat easy to determine by simply comparing the binary output (after some searching for the right compiler options from the compiler for that era).
Indeed, the accusations clearly say that there were significant changes to the code, which makes a reverse engineered comparison harder to do.
Instead, the complaint is that the underlying algorithms were re-implemented, instead of being original algorithms.
From a copyright perspective I can certainly see an issue, but that would be between Rajlich and the author of this Fruit I would say.