The jumpseat is for convenience. Get home early, great. No problem there.
If you as a pilot, or your company is benefiting financially from you riding it is a no no.
That is how the jumpseat agreements are lost.
Don't know about the Fed Ex deal, but if you are getting money for being in my jumpseat then I have a problem with it. If you are vacationing or traveling with the family are positioning early or late, I don't care.