I was in process of activating the POV-ray 3.7 addon and there was a warning with the message "this script is RC". What does this warning mean?
RC means Release Candidate that is a final stage of beta version.
The warning is added by the Authors of the add-on in its
bl_info dict, it does not come from Blender itself. Warnings like that are an attempt by the Authors to inform you (the user) about the add-on's state of completion