An anonymous reader tips news that Google has sent out a letter to app developers explaining policy changes for any new apps published on the Google Play store. In-app purchases must now use Google Play's payment system unless it's for goods or services used outside the app itself. They've added language to dissuade developers from making their apps look like other apps, or like they come from other developers. But more significantly, Google has explained in detail what qualifies as spam: repetitive content, misleading product descriptions, gaming the rating system, affiliate traffic apps, or apps that send communications without user consent. Also, advertisements within apps must now follow the same rules as the app itself, and they can't be intrusive: Ads can't install things like shortcuts or icons without consent, they must notify the user of settings changes, they can't simulate notifications, and they can't request personal information to grant full app function.