RadNavigation can be setup to expand on hover (see demo - http://demos.telerik.com/aspnet-ajax/navigation/functionality/expand-on-hover/defaultcs.aspx).

However, when the menu is collapsed to the More (hamburger) menu this functionality is lost. If the nodes don't have a navigate url they can be clicked to open the sub menu, but if they are set to navigate then clicking will navigate instead of opening the submenu.