Barely. It was originally a XFree86 project called XDarwin, adopted by Apple as a beta release for Jagwire in 2002, was an optional install in Panther and Tiger, default install in Leopard~Lion, and then was abandoned again in favor of the community-supported XQuartz after 2011:
https://xonx.sourceforge.net/ “XFree86, a free implementation of the X Window System, has been ported to Darwin and Mac OS X. […] Our work has been included in Apple's X11 for Mac OS X. ”
Barely. It was originally a XFree86 project called XDarwin, adopted by Apple as a beta release for Jagwire in 2002, was an optional install in Panther and Tiger, default install in Leopard~Lion, and then was abandoned again in favor of the community-supported XQuartz after 2011:
https://xonx.sourceforge.net/ “XFree86, a free implementation of the X Window System, has been ported to Darwin and Mac OS X. […] Our work has been included in Apple's X11 for Mac OS X. ”
https://macintoshgarden.org/apps/x11-jaguar
https://www.xquartz.org/