[my123]

A modified version of Hyper-V called NanoVisor is used. Apps run in SystemOS, which is already accessible officially even through other ways... GameOS and HostOS use a stripped-down version of the NT kernel, compiled differently and without binary compat.

[TazeTSchnitzel]

Yes, can't anyone make a Windows Store app for Xbox One?

[my123]

Anyone can, that's right ;) Every Windows Store(UWP) app that isn't a game* is automatically pushed to Xbox devices also, except if the developer opts out.

* for games, it's separately handled for validation