If you're installing Circle² on macOS and you get an error message that says the program cannot be opened, here's what you can do.
1. Navigate to System Preferences > Security & Privacy under the General tab.
2. Click Open Anyway to confirm your intent to open or install Circle².
3. Then, when the message reappears ("can’t be checked for malicious software...") you can click Open and you will be able to use Circle² as an authorized app on your computer without issue.
💡 There's more info on this on Apple's site here.