April 12, 2016
This error appears due to the Gatekeeper security feature included with OS X 10.8 (Mountain Lion) and later.
To bypass this, open System Preferences and click Security & Privacy. Change "Allow apps downloaded from" to Anywhere.
Once done, try running the installer again.
If you prefer to keep Gatekeeper on, you can always revert this setting to default after installing your iZotope product.