SynPPC:

SynPPC is ARDI's not yet released PowerPC CPU emulator. It will probably never be finished. It was designed to allow other CPUs to run instruction streams meant to run on Motorola's MPC750 (G3) line of CPUs.

Although I've never downloaded or seen it, PearPC can emulate the PPC and could, in theory be made to run a version of Executor that would use PearPC to run the binaries and a natively compiled ROMlib to provide the Classic/Carbon APIs.