It is alleged that he signed up for guest accounts on their network with different laptops, changed his MAC address and re-registered if the IP he was using was blocked (by JSTOR) or cut off of the network (by MIT), and finally connected a laptop in a basement networking closet.
I guess you could say that is 'hacking' in the unauthorized access sense, but not in any meaningful sense. It isn't breaking and entering if someone repeatedly trespasses somewhere (say, banned from a store) even if they change their clothes to avoid detection.