This morning a friend of mine has pointed me on a new release of PearPC, a good Power PC Emulator capable of running most PowerPC operating systems (also under Windows platforms).
The new 0.2.0 version addresses one of the main limitation of this software before... The network now also works with Windows as host and now you can switch the screen resolution at runtime.
I think I have to re-test it, expecially to try DotGnu under Mac OS!