Just what is driving MS to play this game? I can't see p1$$1ng off half the world can be in their interest.
Desperation. For some years in the 90s, Windows was really the only game in town for consumer use. Macs didn't have the software, Linux was a hackers' toy, and Unix was ten times the price. Microsoft had it easy, and people queued up to buy the new version of Windows.
Now, most people will be happier with an iPad than a Windows PC, and they can't even give away the new version of Windows. Microsoft are desperately trying to find some way to remain relevant, and lock users into Windows before it's too late. They've already locked down the PC BIOS to keep other operating systems off 'their' hardware, now they want to lock down applications so they can only be installed through their App Store, and you can't just keep running the same old app on the same old PC that you've had for years. Subscription fees for Windows will surely be next.