Starting with OmniFocus 2, our app uses a single download file that offers both Pro and Standard feature sets. Pro features are unlocked when the appropriate license is entered or registered to your Omni Account, but the application will still be named OmniFocus in the Finder, Dock and Menu Bar. You should be able to confirm that you’re running Pro from the OmniFocus menu. Click About OmniFocus, and look for the purple text box confirming that Pro has been purchased.
You can also confirm that Pro is activated by seeing if you can access any of OmniFocus 3’s Pro-only features, such as Custom Perspectives, Forecast Tag, or Focus mode.