Am I allowed to change the title of the pages and the "box title" on the login page? If I can, how would I do that?
Well, what do you mean? You want to chnage the product name? "RoundCube Webmail" ? and what do you want to do with the box, can you explain it please ???
You can change the title to what ever you want. Look in the config file for $rcmail_config['product_name'] the value of that will be displayed in the page title and on the login screen.