I just got O2 to run on OSx via mono, and here is the proof:
Find an O2 Script
O2 Log Viewer
As you can probably see above I'm controlling which script is executed via the O2_Setup.cs file.
At the moment you can only open the scripts directly since there is some issue with the mono WinForms that crashes when multiple Forms are opened (at least the way O2 does it (with no problems) in Windows))
Ok, so the hard part is now done.
O2 is doing dynamically compilation and most of the issues seem to be on the GUI controls (which we should probably use GTK# when in mono). So for example, the static analysis part should work ok.
If you want to check it out you need to grab the Mono_Branch versions of the main O2 repositories:
And finally, here is first picture of O2 running on another user's box (Dennis Groves), via a GitHub Sync and Mono Develop compilation :)