This gets explained a lot; what doesn't get explained as much is how folks can continue to make money for their work in the "libre" world. It's certainly possible - dual licensing, services, premium editions, physical books, etc., and it's not a bad thing. But my guess is that a "libre" version of this guy's book would rapidly turn into a "gratis" version of it too - a "good enough" PDF would get passed around and ultimately be the main way most people would see his stuff.