Three .js files are used for the scripting. Wouldn't it be an option to combine them in just one external script?
If yes, what influence would that have on the HTML file containing the menu?
Those files can be combined but header of menu.js file shouldn't be changed as it is mentioned in license agreement. Such division into three files was made for caching optimization: menu.js - menu core, always unchangable that's why it is separated. Menu hierarchy can be changed as well as menu level scope settings structure so they are separated from menu core.