After getting several requests to publish the translator scripts, I now packed them and made it available for download at http://translator.roundcube.net/rc_translator-0.1.tar.gz
But don't expect too much. It's just an ugly piece of PHP code mashed up with HTML which I coded once an evening. It is based on the initial work of Yllar Pajus.
The translator retrieves the localization files from the SVN repository and caches them locally for about 10 minutes. In order to work correctly, the local folder named 'localization' has to be writable for the webserver.
Have fun! ~Thomas