But I think it's a mistake to assume that the Play Store is equivalent to your developer footprint for a platform.
Google has been fairly insidious about integrating OS level APIs with the Play Store, so that's blurred the line a bit here - but if the OS is otherwise "Android-like" enough that it's just a matter of choosing a different target in your build and linking to different binaries... it'll be very easy to port over the developer base that's interested.
Seems like Harmony is doing exactly that, and already has a large swath of companies that are planning to support the OS - so while some of that is likely because of government influence in this case... it's not required (ex - I'm thinking of Google and the whole lawsuit with Oracle around the Java APIs)