Please correct me if I am wrong, but my understanding is that Bochs is a Windows emulator. A Windows emulator and a PC emulator are two entirely different things.
Bochs runs under Unix/Linux on x86 machines to eliminate the need for Windows...but when those Windows apps start talking to the x86 hardware, the hardware is there and ready to listen.
Bochs would be useless (in it's currently publicly available versions, anyway) on a Macintosh PPC based machine because then the Windows apps starts to talk to x86 hardware that is really a PPC, it would choke.
Bochs would need to be turned into a full-fledged PC emulator, like Virtual PC, which means instant hits in performance. Unless Apple is working with Bochs AND designing a Virtual PC replacement of it's own, optimized for OS X, I'm not sure we have anything to talk about.