Neverball is free, open-source software maintained by volunteers. We do not participate in Apple's paid Developer Program ($99/year) required to notarize software for macOS, so Gatekeeper will flag Neverball on first launch until you approve it.
Double-click Neverball.app.
macOS will show a dialog saying “Neverball” Not Opened. Click Done.
Open System Settings and navigate to Privacy & Security.
Scroll down to the Security section. You will see a notice saying “Neverball” was blocked to protect your Mac. Click Open Anyway.
In the confirmation dialog that appears, click Open.
Neverball will start normally and macOS will remember your approval for future launches.