I found this one by accident, but it’s more like DOSBox in that it runs 68000 executables with an emulated processor and emulated OS. No SHARP ROMs or HumanOS diskettes needed. It’s strictly text mode, but it’s enough to run executables produced by GCC.
The project is over on sourceforge, and unlike any other x68000 project this one is GPL’d. The source code is remarkably tiny so I’d say for anyone looking for a way to sneak some C into something this may be an interesting ‘door’..