I was curious why Spotify wasn't going after Google as well as Apple, since it seems like Google's policies are pretty much the same as Apple's. Google requires you to pay a 30% fee for in app purchases. Google also requires developers to use Google's payment system for in app purchases. On top of all that, Google also offers its own steaming music service, just like Apple.
According to our source, Google allows Spotify to offer a choice of payment methods. Likewise, this person said, Google doesn't prevent Spotify directing its customers to buy a premium subscription through its website, rather than through the app.
So Google does everything Apple does, except it allows developers to redirect their users to a website to subscribe.