There is a newly started Y-DNA Project for the Coursey/DeCoursey surnames. It is open to all males with any variation of the two surnames as well as those who believe that they are descended from a Coursey or DeCoursey. (Females can participate by sponsoring the testing of a male relative.)
The main goals of the project are to learn more about the origins and history of the surnames, identify different family lines and help researchers make connections (and hopefully break through a few brick walls!).
Examples of surname variations: Coursey, Corsey, Courcey, Courcy, Course, Corse, DeCoursey, de Courcey, de Courcy, DeCorsey, DeCourcey, DeCourcy, DeCourse