Nearly correct according to http://www.kuro5hin.org/story/2001/6/19/05641/7357 http://www.kuro5hin.org/story/2001/6/19/05641/7357 the initial code was provided

Nearly correct according to http://www.kuro5hin.org/story/2001/6/19/05641/7357 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)