BezelHUD is a Quicksilver Interface. For more information visit its about page.
Originally developed by Julius Eckert, it is now under development by Ben Cochran.
To compile BezelHUD, you need to add the Quicksilver frameworks to your source trees in Xcode. For information on doing this, see Ankur's tutorial on writing Quicksilver plugins, specifically the section titled "Xcode Preferences: Adding Source Trees"