I am getting started with the Windows Server 8 beta and noticed this in the list of Features Removed:

The Subsystem for UNIX-based Applications (SUA) is deprecated. If you use the SUA POSIX subsystem with this release, use Hyper-V to virtualize the server. If you use the tools provided by SUA, switch to Cygwin or Mingw.

Cygwin and Mingw are open source tools which let you use some Unix tools on Windows. That said, my preference would be the virtualisation route, rather than installing these layers on Windows Server itself.