Since OS X Mountain Lion, the Mac defaults to preventing applications from unidentified developers or sources from being launched. You’ll discover the message in OS X 10.8 when you try to launch a Mac app that didn’t come from a verified source or from the Mac App Store, and you’ll get an alert dialog that says “[App name] can’t be opened because it is from an unidentified developer”.
This new security feature is called GateKeeper, and it doesn’t mean you can’t run those unverified apps on the Mac, you just have to either temporarily skirt the security blanket of GateKeeper, or turn off the app limitations entirely.
Temporarily Get Around “App Can’t Be Opened” Gatekeeper Alert Message
This is probably the best option for most users, since it maintains some security:
- Right-click (or control-click) the application in question and choose “Open”
- Click the “Open” button at the next dialog warning to launch the app anyway
You can do this with any third party app that gives you this warning dialog and open it anyway.
If you get tired of constantly right-clicking apps to open them, return to pre-Mountain Lion levels of app security by turning off Gatekeepers app verification completely.
Disable GateKeeper’s Unidentified App Developer Prevention Completely
This is generally best for advanced users who know what apps to trust and not to trust:
- Launch System Preferences from the Apple menu
- Choose “Security & Privacy” and then click the “General” tab, followed by clicking the lock icon in the corner to unlock the settings
- Look for “Allow applications downloaded from:” and choose “Anywhere”
- Accept the security warning and allow
- You can now launch any app from any location or developer