I really think this is how Stallman thinks. As far as I know, he's never mentioned the words "deontic logic" in writing, but I get the impression he believes he's attempting to give a formal logical argument for morally obligatory behavior.

Aside from the hassle involved with using only free software, I think one of the things holding him back is that he's much better at math/comp sci/logic than he is at social skills, and he's not especially suited to being the leader of a popular movement.