QEMU is a generic and open source machine emulator (x86/SPARC/ARM/PPC etc. on x86/PPC etc<sep/>translation) and virtualizer (x86 on x86 only, near native performances) using a host driver (QEMU accelerator aka KQEMU). FOSS (GPL/LGPL/BSD).
"You don't want the architecture to not be compatible with itself moving forward." -- IBM manages to use the old school Java line about opening PowerPC