Specifically, he committed himself to the causes in which he so passionately believed: internet freedom, civil liberties, making information and knowledge as available as possible. Here he is in his May, 2012 keynote address at the Freedom To Connect conference discussing the role he played in stopping SOPA, the movie-industry-demanded legislation that would have vested the government with dangerous censorship powers over the internet.
Critically, Swartz didn’t commit himself to these causes merely by talking about them or advocating for them. He repeatedly sacrificed his own interests, even his liberty, in order to defend these values and challenge and subvert the most powerful factions that were their enemies. That’s what makes him, in my view, so consummately heroic.