I just downloaded an unsigned app (https://www.bitcoinarmory.com/download/ https://www.bitcoinarmory.com/download/), and I see the usual `"Armory" can't be open

I just downloaded an unsigned app (https://www.bitcoinarmory.com/download/ https://www.bitcoinarmory.com/download/), and I see the usual `"Armory" can't be opened because it is from an unidentified developer.` message, with only an [OK] button to cancel the launch. I see that the video maker disabled Gatekeeper by choosing Open from the right-click menu.