Besides, Google's version of Android is also proprietary software that is not only harmful to user freedom, it's also more and more privacy hostile every day. Yet Google is still held as the pinnacle of open source friendly companies in some circles. Old prejudices, again.
MS is a lot more open-source friendly, and smarter, but it's pretty clear that this is a strategy to get more people tied into ecosystems which favor proprietary Windows. MS is behind, so they're playing catch-up.
Unfortunately there is no real market interest for such a device, so I'll take what I can get.
And I humbly submit that Windows as far from a dying platform. Less popular, sure, the numbers bear that out, but popularity isn't a measure of longevity. If that was the case, OS X would be dead, along with most Unix-like OSs.