The latest Windows 10 Insider Preview build doesn't add much in the way of features—it's mostly just bug fixes—but one small new feature has been spotted, and it could be contentious. Vitor Mikaelson noticed that the latest build lets you restrict the installation of applications built using the Win32 API.
The Settings app has three positions: allow apps from anywhere (the default), allow apps from anywhere but prefer apps from the Store, and only allow apps from the Store. Put in its most restrictive third position, this setting will block the installation of traditional Win32 applications; only those shipped through the Store using the Project Centennial technology will work. Interestingly, the switch only appears to govern installation. Changing the setting to "Store apps only" will allow existing Win32 applications to work, only preventing new ones from being installed.
Microsoft is late to offer this option; macOS has had a similar toggle as part of its Gatekeeper system since 2012.
With this switch, every version of Windows 10 can offer similar lock down to the rumored Windows 10 Cloud edition. This Windows edition, still not officially confirmed by Microsoft, will ship with the switch set to "Store only," and it's expected to require a paid upgrade (to regular Windows 10 or Windows 10 Pro) to change out of this position. This SKU gives Windows something of a Chrome OS or iOS-like experience: legacy applications can't be installed at all, and the Store acts as the gateway to any and all third-party code.
The most recently leaked build of Windows 10 Cloud supports both UWP applications, built using the new Universal Windows Platform API, and Centennial-converted Win32 applications. This should give it a much wider selection of applications, and hence much wider appeal, than Microsoft's last attempt at a locked down operating system, Windows RT.