Dashcode lets you quickly and easily build elegant and compelling Dashboard widgets.
Created to meet the need of widget developers, Dashcode combines powerful visual layout tools with a code editor, debugger, and comprehensive package management into a world-class integrated development environment.
It lets you easily and quickly create powerful and useful widgets for yourself, your organization, or even for distribution to the world.
From the start, Dashboard widgets were designed to be easy to develop. They use the familiar and widely used Web technologies of HTML, JavaScript, and CSS.
Because of the use of standard Web technologies, it's possible to develop a widget using only a text editor, such as TextEdit. However, very few developers are well-versed in creating both great graphical artwork and smoothly functioning code.
As well, it became apparent that the process of packing up a widget and tracking down bugs takes too much time when using just a text editor.
Dashcode was created to address all of these issues.
It takes care of packaging so that you don't have to create a widget's bundle by hand.
It provides a test runtime with a built-in debugger that's a click away so that you don't have to deploy your widget into Dashboard to test it.
And, it provides rich library of graphic elements for you to use to give your widget a compelling design. These features let you focus on making cool, unique, and polished widgets.
Dashcode in Mavericks:
Option 1:
In Finder right click on Dashcode app
Click Show Application Contents
Open Contents directory
Open Info.plist with TextEdit
Now modify the bundle identifier:
<key>CFBundleIdentifier</key>
<string>com.apple.Dashcode</string>
to
<key>CFBundleIdentifier</key>
<string>com.apple.DashcodeLegacy</string>
Done.
You can now open Dashcode without any Terminal tricks.
Option 2:
Go to your Applications folder, right click (ctrl click) on the Dashcode app,
click Show Package Contents
and in there go to the MacOS folder.
Click the “Dashcode” terminal application in that folder.
Dashcode should now launch… along with a terminal window, you have to wait a bit.
That’s it… it should work… you still get the horrible cross sign on the app though. And it might ask for your permission to access you Contacts and everything else.
Note 1: You can drag this terminal app to the desktop to create an alias directly to it, this way you get a faster way to launch it.
Note 2: To close the app, first quit Dashcode, then quit the Terminal app.
DevCenter 
TheDashboard 
