1) Cockpit Jump-seating is pretty much limited to flight crews and aircraft dispatchers. CASS is required for OAL personnel to actually ride in the cockpit j/s. Some airlines require CASS participation to get on the airplane at all. There is an program that allows international cockpit jump-seats, but it is pretty much limited to freight dawgs.
2) Flight attendants can jump-seat on FA jump-seats if there are any available. There are some airlines that allow OAL FAs to jump-seat, but 90% is own airline.
3) Usually, cabin seats are issued to jump-seaters if they are available.
4) All jump-seating is a form of non-revenue travel.
5) The majority of non-rev travel is by employees on passes, ID90s, ID50s, zone fares, etc.