I doubt it is even financially worth it for Kap to sign a contract for a backup job. IMO, he's better off financially by acting like teams are colluding against him (they are hence the settlement).
If the Raiders won't sign you, nobody will and the Raiders sign anyone regardless of their background (Brown, Incognito and Burfict to name a few pariahs). He was probably better off with his publicity stunt because the NFL just wants him to shut the fuck up and go away.