There is nothing to copy. They cannot just copy a code from an existing key. The PIN they are referring to is more of a password to access the skim.
The keys have RFid chips in them and are hard coded with a unique id like a serial number. No two keys have the same id...ever. You have to program the module in the jeep to recognize the unique id in the key. Again, the module in the jeep is programmed, NOT the key. With two working keys, you don't need the PIN or DRB, using the existing keys you can access the skim and then program it recognize the new key. But if you only have one key, the only way to do this is with a DRB. It is rare that a run of the mill locksmith with have a DRB, but they are out there.
But again, you cannot just "copy" the RFid from one key to another. You have to tell the module in the jeep which RFid's to accept.
Sent from inside my dinosoar head.