You'll notice that Joel has never addressed the funding issue...
I had actually looked into this before, but without a smoking gun(Joel admitting that jw's primarily funded the film), there isn't much to go on except a theory. This would look great in the press -- having someone come forward and say that the Reibling and Zaremba families funded this film. So much for an 'unbiased' piece then, right? Of course, Joel would never reveal the true financing if this theory were true. It would give him a terrible reputation for being a sellout film maker.