"....to get its service on as many apps as possible, it is launching an affiliate program to offer up free credits to developers who get people using its service."
If they aren't offering a cash percentage, I don't think they're going to find many takers. I certainly wouldn't integrate a new API in exchange for Uber credits.
Edit: On the affiliate page, it says "Cash rewards coming soon" but it seems rather odd that they wouldn't launch with that. Generally affiliate programs pay money.