Hey Ronny,
Sorry, the Xojo/Real Studio article hasn't been updated to follow the new walkthrough that we have on the other languages. The "IsGenuineEx() function" is just what it's called in C/C++. In Xojo, it's just the overloaded IsGenuine() function (the one with 2 or more parameters).
Follow the example project -- it shows best usage. We'll also get to work on the documentation.