Sometimes, Gatekeeper is not your friend…
After installing a new program on my Mac Mini/Sierra media server, the program was verified by Mac’s Gatekeeper program. Apparently, the program failed the verification, as I got the dreaded error message: “Program Name is damaged and can’t be opened. You should move it to the Trash.” This seemed like a great time to install my favorite file browser MuCommander, and do some investigating. Adding insult to injury, Gatekeeper provided the same message for the MuCommander install. Enough installing, time for some digging, and I found two ways to work around the Gatekeeper.
Solution 1. Create an Exception for Gatekeeper
From a Cnet post, I found an article by Topher Kessler that explains how to create a Gatekeeper Exception for a “damaged program”. Here’s how it works:
Open the Terminal and type the following (do not press enter yet):
sudo spctl –add –label “NAME”
In the above command, replace “NAME” with a label that you would like for the rule, which you might consider setting to the program name for relevance (for example, you might name it “Word” for Microsoft Word).
Make sure there is only a single space after the “NAME” portion of the command, and then drag the faulty application to the Terminal window. This will complete the full path to the program, so the command should appear like the following:
sudo spctl –add –label “NAME” /Applications/Program\ Folder/Program.app
When finished, press Enter to execute the command, and an exception for the program will be created that will allow it to run. Now you can double-click the program and open it directly, and should not be met with a damaged-application error. Again, do keep in mind this routine will bypass Gatekeeper checks for the specified program, so only do this if you know the Gatekeeper warning is simply a false positive .
Solution 2. Give Gatekeeper A Vacation
This solution is probably best used if for some reason the above solution fails. Open a terminal and type:
sudo spctl –master-disable
This simple command disables the program security assessment subsystem on OS X. More simply put, it turns Gatekeeper “off”. With the Gatekeeper on vacation, your system will be a lot more vulnerable to attacks. Know what you are doing before using this option. You change “disable” to “enable” to turn Gatekeeper back “on”.
 https://www.cnet.com/how-to/how-to-bypass-damaged-application-warnings-in-os-x/ | Topher Kessler