Windows Cloud: Part 3!
At the end, Windows Cloud is nothing more or less than a Professional variant with UMCI enforced.
As such, its compatibility with existing Windows software* is only and solely prevented by having UMCI enabled and active.
Rumours of Win32’s death are exaggerated to say the least, Windows itself relies on it.
* Centennial apps do not run in an AppContainer, so they are subjected to the UMCI signature checks.
A hacky way was implemented in some cases, through SmartScreen, but that’s quite easy to workaround. There is no lists of disallowed programs anywhere, it’s done fully via code signing.