"I have a, um...FRIEND who's done some pirating..."
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"Is he going to get sued? Arrested? Expelled from Trinity? What do I does he do now to stay out of trouble?"
Is your "friend" going to get sued? There's no way for us to know that. But there's always a chance, and Trinity won't defend you--I mean, your "friend"--if he does. So he shouldn't risk it. He should delete his BitTorrent and any other file-sharing clients from his campus computer (ITS has a helpful guide on how to do this), any illicitly downloaded files, and he should stay away from websites like The Pirate Bay and Mega.
And above all, if he's contacted by any university official regarding a DMCA notice or other copyright infringement activity, he must follow their instructions exactly.