I asked this question via email support. Here is the answer from WPMUdev support:
"Our directory will work on both Single site and Multisite. We provide the plugin with a default Directory theme integrating all the cool features, great look and feel you can achieve with this plugin."
So, I went ahead and paid for 1 month of membership and downloaded the plugin and installed it. It does NOT seem to work with a single install. Following your tutorial, none of the options are available - like Network-Admin. I don't see any options for setting it up.
Can someone please clarify if it will work on a single install. And if so, can you give me instructions on how to use it?
Thank you for your help.