But the ad and in-app revenue streams mentioned in the article suggest that they have also been active in other fields. In-app purchases that still go on after account termination might be a hint in the right direction though: would IAPs via Play still be going on? External ("untaxed") IAPs are the biggest sin from the app-store's point of view. External purchases are allowed to be handled externally (e.g. paying for physical goods in the Amazon app), but definitions are not always clear and then it's all arbitrary judge-and-executioner.