The first time you open the file, right click on it and select open. In the future, the application will open without confirmation as it has been approved.
"This is by far the easiest and most secure method...To open a file blocked by Gatekeeper simply right-click the file in question or ctrl-click, and in the menu which appears, select Open. A prompt will now appear asking for confirmation.
In future, the application will open without confirmation,You only need to do this on first launch. This method works for both the “x is an application downloaded from the Internet. Are you sure you want to open it?” and “x can’t be opened because it was not downloaded from the App Store” prompts, and leaves Gatekeeper enabled at all times.
SOURCE
http://www.idownloadblog.com/2017/04/20/fix-application-from-internet-gatekeeper/
https://www.unlockboot.com/application-downloaded-internet-sure-want-open/
-bash: /System/Library/Frameworks/CoreServices.framework/Versions/A/Frameworks/LaunchServices.framework/Versions/A/Support/lsregister: No such file or directory
Is that the correct command? I'd appreciate it if you could repost in pastebin.com – blogjunkie Sep 1 '12 at 9:20