Anyone know what the underpinnings are of Longhorn / Vista? Is it UNIX based or still M/S proprietary?
Its still the same NT kernel.
Windows NT. One of the original designer/developers for NT had something to do with Digital's VMS. Anyhoo, the Windows NT kernel was originally supposed to be a microkernel, quite unlike traditional Unix kernels. I doubt the Windows kernel can be called a "microkernel" anymore, though. Naturally, Windows NT, VMS, and Unix kernels are all multitasking by design, but the way that NT/VMS start new programs is also different from the fork() and exec() approach that Unix uses. People who insist that the spawn approach is better are probably full of it. As far as most users are concerned, though, Windows NT is designed to look a lot like MS-DOS, a really crumby OS that lives on even after death. Windows ain't Unix. There are plenty of free "Unices" to choose from, plus OS X, which will cost you. Windows is proprietary in the same way that the pope lives in the vatican and bears poop in the woods.