ClaudeUsage is not distributed through the Mac App Store.
Follow these steps to open it safely.
Open the downloaded claudeUsage.zip file. This will extract ClaudeUsage.app.
Right-click (or Control-click) ClaudeUsage.app and select Open from the menu. Do not double-click — that won't give you the option to proceed.
macOS will warn you that the app isn't from the App Store. Click Open to confirm. You only need to do this once.