Microsoft's Windows Subsystem for Linux is coming to all Windows 10 users (archive):
You won't have to be a tester to try Windows 10's new, built-in Linux kernel in the near future. Microsoft has confirmed that Windows Subsystem for Linux 2 will be widely available when Windows 10 version 2004 arrives. You'll have to install it manually for a "few months" until an update adds automatic installs and updates, but that's a small price to pay if you want Linux and Windows to coexist in peace and harmony. It'll be easier to set up, at least -- the kernel will now be delivered through Windows Update instead of forcing you to install an entire Windows image.
Embrace, Extend... Excite!
Windows blog post.
Previously: Windows 10 Will Soon Ship with a Full, Open Source, GPLed Linux Kernel
I'm pretty sure that Microsoft would prefer you to use Windows, but if you're going to use Linux then they want you to use their Microsoft Linux on Windows instead of installing Linux on the bare metal. Kind of a variation on the old days when Microsoft would prefer you buy Windows, but if you aren't paying for your operating system then they'd rather you pirate Windows than install Linux.
In the early Groklaw days, I used to joke about this exact scenario. Never taking my joke seriously. Now here it is upon us. Just like the one time joke that you couldn't get infected with malware by merely receiving an email into your inbox.