Hi, I can't recall if I purchased a license or not. Is there a way this can be checked?
I've just checked and I don't see any order that references the email address you've used when registering with the community forums. You might have used another email address, if you have multiple.
Maybe you've bought via the Mac App Store? If so, you can check via the Mac App Store app. Make sure you're logged in with your Apple account — the icon on the lower left should show you name. If not, you'd need to login via ⌘0 where you can also see all of your purchased apps and can download Mp3tag via the respective icon.