I've used JSTOR and I never agreed to any TOS. More than likely, the University in question did that as they are the actual "customer".
I frankly find it hard to believe that spoofing a MAC address to keep from being banned from a network rises to the level of "hacking". The guy already has trespassing charges for being in the building, and that seems like the most appropriate crime to charge him with. Everything else is just piling on bullshit because "We didn't have a law that fit this guy, so we're gonna throw everything we can think of at him because we think he should go to jail."
For the record, all the articles he "stole" are public domain. JSTOR asserts copyright because it was their scan, even though the articles themselves belong to the public now. The problem is, that there's currently no way to access a lot of this older public domain stuff except by going through JSTOR.