For others coming along later, right click, pick "open". If you don't get an "open" button on the dialog, go to system preferences, security, general. You shoul

For others coming along later, right click, pick "open". If you don't get an "open" button on the dialog, go to system preferences, security, general. You should see a button that says "Pharo Launcher wouldn't open. Open anyway" or something of that nature. Click. Profit!