I'm not yet sure what is the best approach to use this loader. When I started looking for examples I sent a small tweet which was replied to by Stefan Koopmanschap as he used this class loader in one of his own libraries. What he did is to include the class/namespace registering code in one of the central classes of his library. If you take a look at my code you will see the same approach.
He decides that the library itself shouldn't try to do the autoloading itself. It should always assume that there's something in place to load the files/classes it needs to get the job done. The UniversalClassLoader is prefect for this but, in his option, shouldn't be a part of an application's functionality (see his commit here removing the autoloader).