Sorry but that seems a bit pointless to me, especially since you ask specifically for an OS4 port... why would EA care for half a second about an OS that's not even released? Come back when there will be an established market of hundred of thousands users, and then EA may bust a move...
Asking for an open source release would have made more sense I think... At least it could be ported to Windows, Linux and Amiga OS with RTG support... but then I imagine the original code would be a nightmare to port... So maybe it's easier to start a clone from scratch
there were some pretty good attempts on PC some years ago (Grafx2, VGA Paint)... and on Amiga PPaint is free now. Does/will it work on MorphOS/OS4?
