TWE-
You are correct. OAL jumpseaters on International flights may not sit in the actual cockpit jumpseat, but must sit in a cabin seat; as is the policy at every other airline. Luckily, it is unlimited cabin seats as long as they are on the AirTran reciprocal jumpseat agreement list.
Note to all: For DOMESTIC flights - if a Gate Agent tells you that you have to go list at a Customer Service Desk on the concourse, they are just being lazy. That is not the policy. Gate Agents, per their own policy manual, are required to list you at the gate as long as you arrive prior to 10 minutes before scheduled departure time. If you encounter any problems like this, ask to speak to the Captain. If the gate agent won't let you do this, or the Captain is not available, ask any passing AirTran pilot for help. He/She can go down any jetway and ask the Captain to come up to the gate to resolve the situation. Then make sure you document the incident with your J/S Committee and ask that they forward it to the ATN J/S Committee.
For INTERNATIONAL flights - If you are arriving into a AirTran hub airport from which international flights depart (ATL, BWI, MCO, MKE) after jumpseating there on another airline, you will most likely have to go to a Customer Service Desk (located inside security, not outside) first to pay your international departure taxes. You can try doing that at the gate if you want, but you may not be successful. If you are arriving at any AirTran airport from home, hotel, etc., you can take care of all of that at the AirTran ticket counter for that airport (the preferred way) , or you can proceed directly to the gate for the domestic portion of your flight and then when you get to the hub airport for the connection, you can go to the Customer Service Desk there.