Airplay stuff never talked to Apple's servers though, this does.

If Apple wants it gone they have a legal staff that can make life hell for the app author. My guess is the 'iMessage' name and icon design are enough for a takedown order.

I understand that with the latest Apple TV update Airplay is now proprietary. Ie. wrapped in Apple's FairPlay DRM spec. So, any third party non-licensed Airplay services are now dead.

With the US' draconian DMCA law in place, it also now illegal to build any devices that Apple hasn't licensed to use Airplay on your Apple TV.