Wikipedia
Dashcode
Dashcode was a software application created by Apple Inc. that was included with Mac OS X Leopard and facilitates the development of widgets for Dashboard. It was first included on new MacBooks shipping around the time of May 24, 2006, as part of the Xcode developer tools.
Dashcode, Version 3.0 (328), was included as part of Apple's Xcode developer tools on the Mac OS X Snow Leopard DVD as an optional install.
The last iteration of Dashcode, Version 3.0.5 for Xcode 4, is still available to developer account holders as an optional install from Downloads for Apple Developers (Apple Developer ID required).