The patch adding ruby support did not touch any C++ code. It did touch some ui files and Qt Resource files. It would be possible to add extra language support without even recompiling the application if not for the Qt Resource usage. Part of the intent of that example application though is to show how to use Qt Resources with Grantlee though, so that is not going to happen for that app :).
Grantlee version 0.1.3 now available