Before, you needed to sign with a "developer ID distribution" certificate if you wanted to avoid having to tell users to "ctrl-click DMG then click open" to bypass gatekeeper. This certificate required a paid developer account.

Now you can still distribute un-signed, un-notarized software and tell users to ctrl-click open to bypass gatekeeper. All this does is require notarization (Apple running malware analysis) to have it run without a ctrl-click.