It is composed of code derived from NeXTSTEP, FreeBSD, other BSD operating systems, Mach, and other free software projects’ code, as well as code developed by Apple.
Which makes Darwin a system with BSD elements, just like some versions of Windows and all versions of Linux. Windows and Linux aren’t BSDs, I think you agree; neither is Darwin, for the same reason.
So Wario is OpenBSD and Waluigi is Darwin?
Darwin is not a BSD.
https://en.m.wikipedia.org/wiki/Darwin_(operating_system)
The kernel is not BSD. That’s like running GNU software on a BSD kernel: It’s still not a Linux.
You could have at least skimmed it.
Which makes Darwin a system with BSD elements, just like some versions of Windows and all versions of Linux. Windows and Linux aren’t BSDs, I think you agree; neither is Darwin, for the same reason.