Not much yet, however. It gets really messy around the time dos.library gets into the picture. If good compatibility is desired there's a lot to do there.
Now that the easy part is over the real work can begin.
The DOS.library changes were already slated for the AROS ABI version 1.0 branch. That suggests that there will be some teamwork involved as well.
It will be work but it'd be a lot easier if some of the team could grant SVN access to the repositories. Toni Wilen is still waiting and so am I. It's a shame that the AROS team encrypted the SVN so that nobody could browse or download anonymously.