Reviewing the Platform
The scheduling solution is based on the Group Work Lists site feature in SharePoint, which is available on all the various platforms from Office 365 Small Business through the SharePoint Server Enterprise edition.
If you find the scheduling functionality useful, it might be worth your time to look into the other lists that are created as a part of this feature: Phone Call Memo, Whereabouts, and Time Card (via SharePoint Designer).
Although the scheduling piece works by using the Resources list, it could also work with actual system users. System users would allow for more audience targeting and other useful views and functionality. One of the other lists, Phone Call Memo, could also ...