If you run across this error message while opening Mariner Write, follow the simple steps below to get beyond the error.
-Go to your System Preferences
-Got to Security & Privacy tab
-Then, in the bottom section, click the "Anywhere" button in the "Allow Apps Downloaded From". You made need to unlock and lock via clicking on the lock icon in the bottom left corner for the setting to become active.
You should be able to launch Write after making this tweak to your system. Once you are done opening Write, just return that setting to it's default setting if you choose.