To reproduce:
Create a SQL table as per this article - http://www.telerik.com/help/winforms/scheduler-data-binding-using-datasource-property.html . Add the following mappings using EntityFramework or OpenAccess - http://www.telerik.com/help/winforms/scheduler-data-binding-using-datasource-property.html. You will notice that the resources cannot be mapped.
Workaround:
Implement a One-to-Many relation by adding a ResourceId column in the database and removing the old table.

Resolution: Both EF and TDA mappings work. Due to the differences in the mechanisms of the two products there are some slight adjustments that need to be made. Below is how to set up the mappings with EF and in commented code for ORM.
SchedulerDataEntities1 entityContext = new SchedulerDataEntities1();