Okay, I guess as someone with hard-won expertise I'm duty-bound to take slight exception to this line: Put a backpack on and you can walk into any building at any university in the United States any time you want. First, the nitpicking: Technically you can't get into Harvard's excellent libraries without actually (a) being a Harvard student, or (b) working for Harvard. (And if you're a programmer, I'm not sure which…
In a literal sense, no, that's not enough. In a practical sense, if you're serious about doing research and have the necessary background to be able to do good research, finding a faculty member who will invite you to join their group as an unpaid "research assistant" is trivial.