I saw before on this site a screen shot which was taken for a schematic drawn on spectre, but the operating system was windows XP (as I saw the start button, the quick launch icons, ...)
You can run Cadence from a windows machine by connecting to a remote machine which would actually run cadence. This can be done using XWin32 or Exceed.
Hope this helped
Like XWin32 will open an XTERM panel and then when you start Cadence from that panel, it will open cadence but you will actually See the windows title bar on it. So on a screenshot it will look like its running in Windows.