If you try to open an app that is not registered with Apple by an identified developer you get a warning dialog.
This doesn’t necessarily mean that something is 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.
Step-by-Step
To override your security settings and open the app anyway:
- In Finder, locate the app you want to open.
- Hold down the Control key and click the app icon, then choose Open from the shortcut menu.
- Click Open.
The app is saved as an exception to your security settings, and you can open it in the future by double-clicking it just as you can any registered app.