Phil: Different hostels have different rules, but the simple answer is no, it is not necessary to be a student to stay at a hostel.

Colin: I have no particular preference for hostel chains/independents, but I'm just stating from experience that HI is a reliably clean place in Vancouver. I haven't been to any hostel in north america that had any curfew or ridiculous rules. Wash your own dishes seems to be the extent of them. I hear things are different in europe, but I've sadly never been. Soon, though, I hope.