According to Windows Blog Italia, which said they've had a chance to test the current version of Windows 10 Cloud, the product can run Windows Store apps only. The site noted that Windows Store apps built using Microsoft's "Centennial" Desktop bridge, which enables developers to move their Win32 apps to the Windows Store, work on the version of Windows 10 Cloud to which they have access. UWP apps and Windows Store apps have not been synonymous terms. But the important point here is Windows Cloud will be locked down so as to prevent users from installing apps that are not in the Windows 10 Store, which can be seen as a plus from a security and manageability standpoint, but a minus given the less-than-robust collection of UWP/Store apps available for Windows 10. Microsoft is believed to be planning to position Windows 10 Cloud, at least in part, as an alternative to Chrome OS and Chromebooks.
Microsoft's Windows 10 Cloud version: Alleged screen shots leak | ZDNet
Microsoft's Windows 10 Cloud version: Alleged screen shots leak | ZDNet