SheepShaver is a MacOS run-time environment that allows you to run classic
MacOS applications. This means that both Linux and MacOS applications can
run at the same time (usually in a window on the Linux desktop).
If you are using a PowerPC-based system, applications will run at native
speed (i.e. with no emulation involved). There is also a built-in PowerPC
G4 emulator, without MMU support, for non-PowerPC systems.