A lot of Windows NT was based on work Dave Cutler had done on VMS and RSX-11, so while I'm sure most of the code was new, the ideas are of a similar vintage to Unix.
Frankly it seems like nothing really new has come out of computing in decades. Basically all the container hoopla happening right now were in use on mainframes before Torvalds released the first Linux source code.
From what I understand, Dave Cutler would probably strongly disagree with that statement!
> while I'm sure most of the code was new
Is there any reason to believe less than 100% of the code was new?