Zynga released this week an open-source project called PlayScript, allowing ActionScript 3 developers to target mobile platforms leveraging the Mono runtime. For the context, Mono is an open-source implementation of the .NET runtime, with support for C#, F# and other languages. You want to develop or reuse a library developed with these languages? Like an AI library using beautiful F#? No problem. (F# anyone?)
Mono, allows you to target mobile platforms through static compilation of your code to native, for info, Mono is the runtime powering Unity and the Xamarin offering for application development.
Zynga created the appropriate bindings so that Stage3D can be used, which allows you to use libraries like Starling, Feathers with it and run your Stage3D code untouched, but don't expect to see the whole Flash runtime libraries to be there, but if you are a game developer, you should be all set. Also, by using PlayScript (AS3 on steroids) you can leverage additional types that the Mono runtime gives you that would also find in C#, like float, short, byte and more.
Anyway, go check it out. This is great stuff.