Our applications are distributed in two different ways: the storefront on our website, and the Mac App Store. These apps are functionally identical, aside from the way that they’re licensed. Apps purchased through our storefront require a license in order to run, whereas Mac App Store versions do not; they instead are tied to the Apple ID you used to purchase.
In order to determine where your app came from, open the Menu Bar and take a look at the contents. Omni Store menu options will include the Check for Updates… and Licenses… options. In contrast, Mac App Store copies will not offer these two options (as the App Store itself will take care of licensing and updating our software).