Kites and Wire controlled model aircraft are excluded from the rules, you just need to read the regulations its all there. And no, a hang glider can not be considered a kite, as it's not controlled by a tether to the ground. The only rules for kites are no more than 400ft high or within 3 nm of an airport, and not to create a public nuisance. You would probably be charged under danger to air navigation were you to impact your kite into any low flying aircraft.