Exactly. People often forget that Congress can only exercise a limited domain of enumerated powers. The big one is regulating Interstate Commerce, which is already huge because of how interconnected the country is today, and is even bigger because of creative stretching of its reach (did you know that the Civil Right's Act's ban on discrimination by businesses is within Congress's Interstate Commerce power, because somebody might patronize your business from out of state?).

Anyway, I suspect Bob Hacker has a strong case that such a law as applied to himself would be beyond the scope of Interstate Commerce. Until he tries to sell or make his OS widely available, at least.