[JonFish85]

Except, much like Apple's walled garden approach, they want to ensure that what is in their app store works. Because if I pay for a product at your store, and it doesn't work, I complain loudly, demand things, etc. That's a headache to deal with, for Google, for the app developer and for someone using a stock phone looking at an app with terrible reviews.

So in a way, they do have an incentive to make sure that unknown builds can't access their app store.

[fnordfnordfnord]

It is a pretty easy distinction for users to make. Google can easily add a disclaimer that Google won't support or guarantee performance on non-Android devices. If they want to keep CM users happy about that they can offer trial versions so that users can test, or maybe even offer a money-back guarantee for an app.