AFAIK only the network stuff was, up until XP and Server 2003. They rewrote all of that for Vista, partly because the original code didn't keep up well with newer developments.
Nearly correct according to http://www.kuro5hin.org/story/2001/6/19/05641/7357 the initial code was provided by Spider but since NT3.5 it's been mostly (see the article for why I say mostly) MS code in the kernel (and the userland code is BSD 'cos it works and ain't broken)
The EULAs used to include sections about the regents of Berkley, but I can't find that in the Windows 8 EULA.