jammr is currently not in the App Store. macOS will display a warning that jammr comes from an unidentified developer when you install it.

Here are instructions from Apple on how to give it permission to install:
https://support.apple.com/guide/mac-help/open-a-mac-app-from-an-unidentified-developer-mh40616/mac

Thanks for posting the work-around.

I'm a developer and have a Mac and Apple dev account. I'm down with helping get jammr certified and in the App Store.

Robb Shecter
robb@public.law

Thanks Robb! The next jammr release will be notarized so that this workaround won't be needed (the beta is already notarized).