@gollum,
I'm sure these same questions were asked about students protesting the Vietnam war. Student protests have a long and rich history in the US. Students are willing to speak out and say what a lot of the rest of us are to comfortable or to afraid to say. The college administration responses have been interesting to observe as well.
As to your questions, yes, some have been arrested (although many have been released without charges). I imagine they will receive college credit if they complete their coursework. Some universities are threatening reprisals against the students as well. USC first cancelled their commencement speaker because she was Muslim then cancelled the entire commencement ceremony.