If you're using Mac OS Mavericks, Yosemite or later you may need to update the setting to permit running Arduino IDE

1. Open the, System Preferences from the Apple Menu.
2. Open the, Security and Privacy control panel.
3. Click on the General tab.
4. Click the Lock Icon and log in
5. Change Allow Apps Downloaded From to Anywhere
6. Open the downloaded IDE.
7. Go back to the Security preferences and change the selection back to Mac App Store and identified developers
8. You only need to go through this procedure once. Mavericks will remember that it's OK to run the app.
9. That's it, you're ready to start using the Arduino IDE with Adafruit's board on OSX!