I might re-phrase this. My impression is that:I think I've always felt that Fabien/FSF would be on tenuous ground for legal action
* Fabien/FSF would be successful in stopping Rybkachess (is this an entity in itself?) from distributing Rybka 1.0 Beta through Rybka 2.3.2a (unless the GPL conditions were met), though likely because VR would not fight this.
This would be one remedy to the putative claim that some versions of Rybka are a "derivative work" of Fruit.
A more difficult claim by Letouzey would be that this remedy is not sufficient, and that in fact VR gained a unfair competitive advantage through this copyright violation (Fruit had gone commercial at the time), making him liable for damages (possibly even for Rybka 3 and Rybka 4, if one were to conclude that this was a "continuing market"). The viability of such a case might depend on aspects of the commercialisation of Fruit that are unknown to me. Finally, even if this were shown, the amount of damages is not clear (recall that Convekta paid VR a salary for some of the period, so for simplicity perhaps they would be named as a co-defendant). One of the more famous anti-competition cases in the US involved the National Football League versus the United States Football League -- the former was found guilty of violating anti-monopoly laws, but the awarded damages amounted to $1 (though this was tripled due to anti-trust law).
For that matter, a really aspiring lawyer might conclude that either Convekta or Yuri Osipov has a case against Rajlich, in that he scuttled their mobile Strelka plans based upon some sort of improper pretense as to the copyright issues.
EDIT: I guess I'm required to note here that I have zero legal expertise.