OO3 Pro is com.omnigroup.OmniOutlinerPro3
OO3 is com.omnigroup.OmniOutliner3
I'm not sure it's the best way to do it, but the following worked for a proof of concept:
Code:
set appID to "com.omnigroup.OmniOutlinerPro3"
set hasOOPro to true
try
tell application id appID
activate
end tell
on error
set appID to "com.omnigroup.OmniOutliner3"
set hasOOPro to false
end try
tell application id appID
if hasOOPro then
display dialog "User has OmniOutlinerPro"
else
display dialog "User has OmniOutliner"
end if
end tell