My response was just to counter the common misapprehension that macOS itself is built on a FreeBSD userland. It's NetBSD, and devices like the AirPort Extreme/Time Capsule use NetBSD directly. And, back when the iTunes Store was a WebObjects service, it was hosted on Xserves running a weird reverse-Darwin (i.e. a Darwin-shimmed userland atop a NetBSD kernel, because macOS itself wasn't yet performant enough to be a good server but they still needed WebObjects to run.)
These days, Apple's datacenters are running all sorts of things, including Darwin, Linux, Solaris, and AIX[1]. But the "Darwin" part is still essentially NetBSD, not FreeBSD.
> My response was just to counter the common misapprehension that macOS itself is built on a FreeBSD userland.
I don't think most people say that macOS is built on top of a FreeBSD userland. Most people rightly point out that there is a lot of FreeBSD code inside the macOS code base specifically the XNU kernel[1].
> But the "Darwin" part is still essentially NetBSD, not FreeBSD.
That's incorrect while there is NetBSD code in MacOS. Dismissing the FreeBSD code, the Mach code, the code Apple wrote and saying that Darwin is essentially NetBSD is extremely disingenuous[2].
