This is a poor menu implementation, squeezebox supports dynamic sizing by default and they should have used it, if you reduce the window to a part screen, the entire active part of the menu, pushes offscreen right and is invisible.
on a scale of 0-10 this implementation is maybe 2
potential to do much more in your implementation of the same freeware
just about any 'vertical drop down css menu's could be used to make this menu,
without flash or java, the flash on the site is just the scroller down the side