Just to clarify, the Mac version worked fine, but I installed the Fallout 2 Restoration mod, and now I'm getting the compatibility mode error.
1. Right click (or Cmd Click) on your Fallout 2 icon and select "Show Package Contents"
2. Run Wineskin.app
3. Advanced > Tools > Registry Editor
4. Browse to:
and delete entry associated with fallout2.exe
Now Fallout 2 should run without compatibility error.
Hope this helps :)