"The app is damaged and can't be opened" message on OS X Mavericks

Problem

Trying to launch the application for the first time, you get a message from OS X telling you that the app "is damaged and can't be opened".

Solution

OS X Gatekeeper shows this message because the application bundle is not digitally signed. To run the application for the first time, you will need to disable Gatekeeper as follows:

1. Go to System Preferences... | Security & Privacy | General tab.
2. Click the Lock icon in the lower left corner and enter your password to make changes.
3. Select Allow apps downloaded from: Anywhere.

You can enable Gatekeeper again after the first successful launch of the application.