Are you pretty sure on that? These are some quotes among others on the topic in a forum discussions back in 2005:
"While Microsoft did technically 'buy' their TCP/IP stack from Spider Systems, they did not "own" it. Spider used the code available and written for BSD, so it doesn't appear that Microsoft directly copied BSD code (which, again, it is perfectly legal and legitimate to copy), they got it from a third party. Also ftp, rcp and rsh seems to have come with the bundle. I have heard that ftp was, but have never used rcp and rsh on Windows, so don't know what version(s) those were or were not included in any particular Windows version.
Anyone can look through the .exes for those files and look for "The Regents of the University of California" copyright notice, if they want to see for themselves (rather than take the word of some anonymous geeks on a forum) ;)"
If Spider engineers didn't even bothered to change any of the BSD userspace utilities what is the chance that they built the entire TCP/IP stack perfectly compatible with the outside world inside the kernel from scratch?
Perhaps you misunderstood my statement I am not talking about NT there, Spider Systems has had their network user spaces utilities and tools but almost all of them were BSD not developed by them. If their tools originally BSD then what were the chances they developed their very own TCP/IP stacks from scratch with good compatibility with the outside world?
This remind me a particular incident happened to Brendan Gregg of the eBPF initiatives, when a company performed a demo of their alleged game changing kernel tracing tools to him and as it turned out the tools were actually Brendan very own developed tools.
"While Microsoft did technically 'buy' their TCP/IP stack from Spider Systems, they did not "own" it. Spider used the code available and written for BSD, so it doesn't appear that Microsoft directly copied BSD code (which, again, it is perfectly legal and legitimate to copy), they got it from a third party. Also ftp, rcp and rsh seems to have come with the bundle. I have heard that ftp was, but have never used rcp and rsh on Windows, so don't know what version(s) those were or were not included in any particular Windows version. Anyone can look through the .exes for those files and look for "The Regents of the University of California" copyright notice, if they want to see for themselves (rather than take the word of some anonymous geeks on a forum) ;)"
[1] Windows TCPIP Stack Based on Unix ?
https://www.neowin.net/forum/topic/381190-windows-tcpip-stac...