Open Source on the Windows App Store

I'm seeing a bunch of articles about the Windows App store being somehow more open source friendly than the Apple App Store, because their license explicitly states something that is true in both cases - that a developer's license can override the app store license.

In practical terms, this is meaningless. If you have an ARM-based Windows or iOS device, you can not side-load an open source application into your tablet or phone. This renders the "open source" nature of the license practically irrelevant, and if publishing a GPL app through either store isn't actually a violation of the GPL it's at least a cynical exercise in Tivoization by proxy.

But what really boggles my mind is that people are arguing that this makes Microsoft more "open source friendly" than Apple. Until I can go to opensource.microsoft.com and download some kind of Windows Core kernel, the way I can go to opensource.apple.com and download a Darwin kernel, the idea that Microsoft's open source support is anywhere near Apple's is ludicrous. Sure, their sources are incomplete - they don't include the GUI sources and some components that would make it trivial to run OS X on non-Apple hardware - but they've kept these sources updated even when people have taken them and used them to create OSX86. I really expected Darwin to vanish when that happened - there's no license requirement for it.