Does this mean that a French author can sue us for using work that he voluntarily contributed to Wikipedia? Assuming the author's work has monetary value more than zero, then the zero we are paying him is by necessity more than 7/12 less than what it is really worth. Are we legally different in this case than a commercial publisher who convinces someone to sign away his rights for much less than they're worth?
Well, at least he could try to sue. I am not sure he would get remedies for a non-commercial use, but he could certainly obtain to forbid you to us his work any longer.