AoN is not getting funding from Paizo, from what it sounds like from the AMA on Reddit, but the increase in traffic means more ad-revenue and more sponsors for the Patreon. Although I suspect that Paizo is pitching something in too (likely via Patreon).
Also from what I've gathered, AoN is planning on getting a more complete version of the various rules online, as well as getting the spell section fixed so it loads far faster (as the Starfinder version runs nice and smoothly). Also reference linking in the pages (like pointing to pre-reqs of feats and classes), although it sounds like they're going to be very particular about how they'll go about it.
I can see why d20pf didn't get the offer - they do their own thing via the d20 store, as well as hosting the various 3rd party content.