Factor 0.83 will be able to run natively on Intel Macs. So far, I've gotten the runtime to compile. This required changing some PowerPC exception handling code. Also, for whatever reason Factor would crash with an illegal instruction error until I changed the retain stack pointer register from EBX to ESI. I'm not sure why EBX cannot be used for this purpose on Mac OS X.
I'm in the process of updating the compiler backend to support the Mac OS X Intel ABI. This requires setting up stack frames in much the same way as the PowerPC and AMD64 backends already do; so a lot of code can be reused. During bootstrap, the x86 image will load the appropriate ABI support depending on what OS it is running on.