The software starts, but I only get an empty window with empty pull-down menus when I click somewhere.

This is a bug related to some of the Apple computers display management, happily easily resolvable:

• Go to the "System Preferences"
• Select "Displays"
• Choose the "Color" Tab
• Uncheck the "Show profile for this display only"
• Select the "sRGB IEC61966-2.1" profile

Now you should be able to launch and use your synthesizer. Don't forget to check Audio & Midi settings first in standalone mode.