OSX never used X server, AFAIK. DPS was available as extension on X11, but it wasn't the same implementation as on NeXTSTEP, where AFAIK even the old 0.8 code

OSX never used X server, AFAIK. DPS was available as extension on X11, but it wasn't the same implementation as on NeXTSTEP, where AFAIK even the old 0.8 code already used Mach IPC for communication with window server.