"Perhaps one reason Linux users bleat so unceasingly for Apple
to switch kernels stems from a pre-NeXT project the company ran
called MkLinux. MkLinux was a version of Mach running Linux as a
process. The project was sponsored by both Apple and OSF/1 and ran
on Apple's first generation Power Macs and some early
second-generation Power Macs. Performance was about 20% less than a
native Linux would have been, but that wasn't the point; Apple was
looking at different ways to create a modern operating system in
the dark times of Copland before NeXT was even a gleam in their
eyes.
"After Apple's operating system woes came to a head in 1997,
MkLinux was all but forgotten by everyone except the long-time
Apple engineers tasked with updating OPENSTEP alongside their NeXT
counterparts. It was a non-starter, but it was the first taste of
Linux anywhere near a Mac; it would be years later that Linux/PPC
or the swatch of PowerPC versions of more popular distributions
like Debian, Fedora, SUSE, and YellowDog came to Apple
motherboards."