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Mac, Can't open unidentified developer app

If you try to open an app that is not registered with Apple by an identified developer (in this case you're trying to open a Laughingbird Software product) you get a warning dialog. 

This doesn’t necessarily mean that something’s wrong with the app. For example, some apps were written before developer ID registration began. However, the app has not been reviewed, and macOS can’t check whether the app has been modified or broken since it was released.

Take a look at this file from Apple:

https://support.apple.com/kb/PH25088?viewlocale=en_US&locale=en_US