[JdeBP]

Actually, there is a native fork. There had to be, as POSIX personality support was a part of the Windows NT 3.1 design. What there wasn't was a Win32 form of fork. The Native API for Windows NT allowed it quite straightforwardly.

[jkrejcha]

Iirc Cygwin used to use it but iirc they moved away from it because they said that it was pretty slow

Though actually iirc werfault uses NtCreateUserProcess() to clone processes when writing out crash dumps to this day