I think Audi paid third party developers, possibly Twitter or Facebook themselves to make a version of the app to work on Audi Connect.
Since Audi have stopped doing this on future cars (starting with Q7) due to apple carplay and other type stuff, there is no point in custom automotive made app systems, so the funding might have stopped and as the platforms develop, it may have just been switched off. Someone on another forum mentioned Facebook no longer works too.