@BigBenAussie
There's a project out there, called the OpenAmiga project, that is focused on the similarities between the three platforms, showing what is necessary to deliver a source file that will readily compile across all 3.
MorphOS is a clone tho, and not a direct port. It has a lot of enhancements to the API's, closing a lot of problem areas found in the AmigaOS. Also, has a new front-end called Ambient, and has MUI a native component of the system rather than an add-on.
