Happy Birthday, StarMaster.
Reaver's Deep was originally detailed by J. Andrew Keith and somewhat published by Gamelords via the Pilot's Guide books and High Passage magazine.
It is currently available from Far Future Enterprises; I think it's a freebie.
Cepheus Engine is Traveller compatible because, as one reviewer described it, it's Traveller with the serial number ground off.
It was just a way to get around the Mongoose restrictions on publishing Traveller product since Mongoose started out releasing Traveller as OGL, and then changed it up.
Clement Sector is based on discovering a wormhole that led to the opposite side of the galaxy so that people could develop sectors outside of the Traveller Universe.