Yes, a native port instead of relying on a POSIX translation wrapper.
Cygwin is compiled for Windows, but the tools require the cygwin DLL. I see no problem with that.
The cygwin DLL is needed since Microsoft does not know how to make operating systems.
Sorry, but that's a bit of an ignorant statement
First of all, you can get a native POSIX subsystem for Windows, if you so desire - last time I checked, it was even free. Whether it's better or worse than cygwin I haven't tested, as I use neither (I prefer win32 tools offering the same functionality).
Second, NT is a very fine piece of operating system, and if you have any knowledge of it's internals, you would agree.
Third, the cygwin.dll has been pretty buggy in the versions I tried, and it's unnecessary extra baggage when you can do native builds instead.