I never realized there were enough bits and pieces of macOS open sourced that
someone could construct an OS from it. Founded in 2007 but this is the first
time I have ever run across it, as far as I can remember. The mascot is
Darwin (original release: 2000) was a fork of Rhapsody, a codename for Apple’s
operating system it got from the NeXT acquisition (along with some guy named
Steve) in 1998. It was based on the XNU kernel, originally developed at NeXT
for NeXTSTEP and was a combination of the Mach kernel (Carnegie Mellon) along
with bits and pieces from 4.3BSD.
The first PureDarwin was called "PureDarwin Xmas" and released December, 2008
as a developer preview.
I just checked and it doesn’t seem like there’s really been much activity over
the last couple of years.