From the project website (accessed 2017-02-06):
GreekKeys 2015 is the latest revision of a custom polytonic Greek keyboard program with accompanying fonts that has long been useful to many scholars, teachers, and students of the ancient and medieval Greek worlds. GreekKeys fonts and keyboards provide easy access to many specialized characters (e.g., for metrics, epigraphy, and papyrology) that are absent from most system fonts and that would otherwise have to be entered in roundabout or obscure ways.
GreekKeys is intended for those with particular scholarly needs and for those who appreciate a simple scheme for the location of the accent characters.
NOTE: The Society for Classical Studies (SCS) is providing GreekKeys 2015 as a service to the scholarly community but cannot provide support to individual users. SCS has reduced the price of this software to reflect the fact that the software is being provided on an "as is" basis. SCS offers and will periodically update a help page for the software.
NB: "service to the scholarly community" refers only to paid-up members of the SCS.