Surely this has been extensively double-checked and there is an explanation, but I'd be interested into what it is. I get the direction the likes of Uber and Lyft are coming from with the "we're just an app that connects 2 people", but the way Kickback is described on TC makes their "loophole" less obvious. I think they may be more geared towards one betting money against another that they can beat them personally, but it's not immediately clear.
I can enter a Magic: the Gathering tournament with a $30 entry fee and 2 players where the winner gets $50. This isn't gambling since it is considered a game of skill.
It would not be legal for a spectator to put money on the result of this match since their skill is not relevant to the outcome.