So you can act without fear of non-payment, more or less. The opposite would have considerably simplified your decision.
And you still soldier on? You mention somewhere else that you thought these guys' star might rise and you figured being in their good books was not a bad idea. Their overwhelming success at a later date no longer seems likely. My solution to your dilemma is to leave this project and all others related to it behind.
Isn't this also about reputation? If KB would leave the others hanging, he might take a hit to his reputation. From what I read here and on hubski in general, he already has a rather good reputation (mixing national tv and stuff like that). But one of the important things about reputation is that you need to tend to it constantly. Also, trying to find the optimal solution for everybody is admirable.