Tim O'Reilly says that freedom 0 is the freedom to choose your own license. Stallman says that "Current copyright law places us in the position of dictator for our code." One could imagine a universe where governments did not impose monopolies on code so that the person who created it had no more control over it than anyone else. Therefore Stallman can argue that O'Reilly's freedom 0 is really a form of state-backed coercion.
On the other hand, in the absence of copyright law, a developer's would be left with the choice of whether to distribute code as source or binary. So the GPL goes somewhat beyond merely negating the effects of copyright law. If we wanted to achieve the equivalent of the GPL in a country without copyright we would have to make a law that it is illegal to distribute code without source. I'm curious whether Stallman actually believes that we should have such a law.
Withholding the source code does leave some power in the hands of the developer but how can this be prevented in a free society? McDonald's withholds the recipe to its secret sauce. That gives them some power over me because it makes it difficult for me to duplicate it. Mutual fund companies presumably have strategies, information and formulae that they withhold from their customers so that their customers are not in a position to run their own funds. Individuals and organizations have a right to secrets, whether that secret be code or chemistry.