Mac OS includes a technology called Gatekeeper, that's designed to ensure that only trusted software runs on your Mac.
Most applications, especially those downloaded from third-party sources will receive a popup warning message like the one below.
You can select the installation package from the Downloads folder, (tap with 2 fingers or right-click) select Open. It will show a different screen with a warning, but there will be an Open button that launches the installer. Follow the steps to complete the installation.
Once installed (MacOS), go to System Preferences > Security and Privacy > Privacy > Click Screen Recording > ensure that Jibble has a check. Do the same for Accessibility.
If you don't see Jibble under Accessibility and Screen Recording, please click the padlock icon at the bottom to add Jibble.