Installation Problem with macOS

[kls835]

On my Mac with M4 and macOS 13, "brew install katrain" displays the following error: "Error: katrain: It seems the App source '/Applications/KaTrain.app' is not there."

So I go to /Homebrew/downloads/ and click on the KaTrainOSX.dmg file to open the KaTrain folder. I control-click on the KaTrain.app file and Open to open the app. I get the following pop-up message: "Apple could not verify “KaTrain.app” is free of malware that may harm your Mac or compromise your privacy."

I've never had a problem with KaTrain up through 1.14 on a Mac with Intel. Any suggestions about how to install KaTrain on an Apple silicon Mac with macOS 13?

Thank you.