It's related to, but not a replacement for. It's a version of Windows Server designed to work with third-party hardware to give a "Microsoft legal" solution to licensing issues while giving additional tools to help with managing the "clients".
The hardware Microsoft were demoing was all HP stuff, but you could use it in conjuction with N-computing hardware.
I really hope I'm right, my heads still a little fuzzy from BETT yesterday. TMcD can correct me if I'm wrong.