I understand that, but it is also implied that the author iterated on a good deal of material provided by his partner and is now calling it his own. That seems a bit unfair also. I don't think we ought to prejudice the other party on the basis that he had the "idea." Yes, execution is more important than the idea, but it probably isn't that simple.

I'd be totally ready to render judgment if I heard the other guy use the idea argument but we need to hear it from his mouth.