Our website provided a free download of dockDoubler X 1.1 for Mac. DockDoubler X for Mac is included in Theming Tools. This free Mac app is an intellectual property of Daniele Krahenbuhl.
From the developer:
dockDoubler, written with RealBasic and AppleScript, simply makes a copy of the default Dock (the Dock in use) and allows you to switch between the two Docks. Obviously the duplicated Dock is fully customizable.
You may want to check out more Mac applications, such as Occurrence Selector, which might be similar to dockDoubler X.