If they are binary-compatible with Windows, I guess they can just use the existing ones.

Is that legal? Are Windows drivers distributed in such a way that they can be used with non-Windows operating systems?

Who cares?

I know this is a loaded question but I mean it seriously. The importance of legal aspects is highly varying, from matter-deciding to completely irrelevant. Especially if you have a government of a souvereign country like russia behind you, legal problems about redistribution or usage shouldn't be a big problem.

Microsoft doesn't really own the drivers. Microsoft just provides its DDK, then the hardware vendors who wish to include their drivers along with Windows are forced to provide the sources for the drivers in cause to Microsoft. Otherwise the drivers are usually made and provided directly, independently from Microsoft, by the hardware vendors themselves. Its safe to assume that the condition for using these drivers is something that has to make the hardware vendors happy (which is whatever sells their hardware).

Aren't the drivers for SAS controllers and other server hardware usually written by 3rd parties?

It's possible, I think, that there's some Windows driver SDK code used by most drivers that has conditions on it.

I presume it can load NT closed-source drivers for the first three.

I dont have any of these on any of my home or work PCs or laptops

Yes. I think their attitude is one of NUMA NUMA YAY!

If that's from the O-Zone song, it translates (from Romanian) "you only don't take me" - was it a pun?