Maybe a violation of TOS, but I guess it's one of these things that would not be enforced at all. Same way as Oracle can't do much about Google using Java or Microsoft doesn't do anything about Wine.

Regarding the second point - that's true. I've heard there are some plans to add payments to the Aurora store/F-Droid (which are alternative app stores) but right now you can't use paid apps.

I consider this to be a plus though - gives me a chance to switch to open-source / self-hosted apps.