Also, it appears that it is indeed about allowing compiled binaries to run unmodified.
> Specifically, Windows Mobile (and yes, that's now officially the name for Windows on phones and sub-8 inch tablets) will include an Android runtime layer that'll let them run existing Android apps (both Java and C++) unmodified.... Astoria will in principle work with any old APK, without requiring the developer to do anything but publish the app in the store—as long as the APK sticks to the APIs that Astoria will provide.
http://arstechnica.com/information-technology/2015/04/29/mic...
> When we spoke to Microsoft about Astoria, the company would not tell us what proportion of the AOSP and GMS APIs would be supported, but it did confirm that it wouldn't be 100 percent; there will be APIs that Astoria does not provide, and accordingly, APKs that use those APIs will not run.
> On the flip side, Astoria will offer some integration points with Windows so that Android devs can, with minor alterations, support features like Cortana in their apps.
It's nice enough in the short term, maybe -- Windows Phone users can get some subset of quickly-ported things -- but in the long-term it seems to doom Windows Phone to second-class status; why would you write a real, native Windows Phone app when you can just do a quick half-assed port of your Android/iOS version? And if Windows Phone is just a platform that has a bunch of outdated, bad versions of some Android/iOS apps, there's not a lot of reason to buy it.