Hello! I'll be sure to look into Mac versions on my end, however, if you haven't already, you can try opening the app again and then going directly to your Security and Privacy Settings, scrolling all the way down, and selecting "Open Anyway" where you should see "The Zium Exposition" - this may bypass your systems security issues with the app.
Also, thank you for your kind words about The Zium Gallery. Thanks for visiting!