I can't catch that before it triggers a "call" to Apple to very the code and do something else? I'm thinking of rerouting to a feature inside my app that's special to users of that code.
You can generate codes to give you app away for free, or to grant a free in-app purchase, but that is all. There's no callbacks from the app store to your app to intercept.
Possibly you could do what you want with QR codes and launch URLs, or by doing camera+OCR stuff yourself inside your app.
Typefaces have never been copyrightable in the US, but digital fonts implementing a typeface have been since the early 90s.