Microsoft has patents and technologies that cant just be ported over to any form of *NIX. You would have to reverse engineer them. Which violates the Terms of Use and is against the law.
Yes Microsoft does have more slack when it comes to some aspects that are educational based and working with *NIX.
Windows 8 is not and will not be using BSD Kernel. It will not be open source.
Sorry but what they want to obtain is already been tried, like Saxon said, with such things as ReactOS and Haiku. But both of them fall far short of anything usable. You have to create the drivers on a piece by piece basis. You still have to get .NET and Silverlight working. You have to get the Windows Installer working. You have to figure out how to create a Registry and have it be able to be used and accessed.
There is so much more but i think that just about covers the easiest aspects. I can vouch for the fact that Windows is more open when it comes to educational purposes, but that does not cover reverse engineering the technology to be ported over to BSD or any other form of *NIX. That is still highly illegal.