The way I've always seen it is if you are a commuter jumpseating HOME it is always personal use of the jumpseat. Same as if you don't have any deadheads and you bum a ride from your domicile to your home. If you've got bank money, use it. If you buy a ticket, then decide to j/s on the same flight or airline, that's where the problems begin.

I worked for a carrier that tried to pull the j/s stunt to save money, but we didn't let 'em. Most guys I j/s with understand our travel funds only get us back to domicile, which isn't necessarily home.