History of Mac Oni
As long-time Mac users will recall, the Macintosh has been through three major technology transitions since 1984. First came the move from 68k to RISC-based PowerPC processors in the early '90s. When Oni began development in 1997, the OS was at System 7, but Apple was hoping to start fresh with a new OS as soon as possible, and acquired Steve Jobs' company NeXT to use their OS as the basis for this OS. The transition from OS 9 to OS X started in 2000/2001, an awkward time for Oni.
In 2000, Bungie was merging into Microsoft, and Take-Two was assuming command of the Oni IP (as detailed in the Oni article). Having been in development years before OS X released, the best that Bungie could do for compatibility was build the Oni application as a Carbon app, meaning it was written primarily for Mac OS 9 but able to run on OS X. Unfortunately the Carbon build was not without issues in the OS X environment.
Then, at the end of 2001, Omni Group released a Cocoa (native OS X) build of the game which they had produced for free. This became known as the Omni build of Oni (now usually referred to as the PPC build). Their new builds (released through 2003) kept Oni stable for several years. However, as computers advanced, a critical bug cropped up on both Macs and Windows machines, where Oni's access of the graphics card at startup caused a crash. Once the patch was figured out in Windows, it was carried over to the PPC build. Other patches were made in time, documented HERE.
However, Apple would later begin their third major Mac transition: the switch to Intel processors, moving away from the PowerPC chip for which both Bungie and Omni Group had built Oni. In 2009, Feral Interactive (Oni's Mac distributor outside of North America) expressed an interest in putting out an Intel-native build of Oni. They obtained the source code from Omni Group, who had begun porting it to Intel, and made a beta release in 2011 HERE. The release is stable, although it has a few non-crashing bugs.