That’s subjective mate. He may be paying nothing for the free advertising but he is also not charging interest on his loan. He’s not taking money out.
Has more to do with the likelihood of Bruce stepping aside in the summer. If you believe the same Twitter ITKs that get the pre match lineups correct, Bruce apparently has health problems and has struggled with the stress of this season (he has remarked on this personally - the commentators on the recent Arsenal game made reference to a comment he seems to have made about "not needing it [the stress] at my age"). Gattuso for no compensation strikes me as an opportunistic Mike Ashley style punt.