I don't subscribe to the believe that users are dumb and must be protected from anything they don't know. Treat users with respect and they usually return the favor and treat you with respect. What's wrong with saying that "Univention is the server operating system we're using"? Do you really think this will fly over the head of people? Do you also hide the product name of all the other applications in use in your company?
To get back to your problem: I'm pretty sure there is no simple way to make the password reset functionality appear with a different URL. You can muck around with Apache's configuration, of course. The file to modify is /etc/univention/templates/files/etc/apache2/sites-available/univention-self-service, the template from which the actual configuration snippet is generated. Change it, run "ucr commit /etc/apache2/sites-available/univention-self-service" in order to re-build the configuration, and "service apache2 reload" for applying it.