Not sure about this particular version, but there certainly are other copies floating around.

One thing to be aware of is that to my knowledge, DEC never released a complete source kit outside of the company at any price (...  we certainly had that behavior in Ultrix/Tru64-land I know for sure...).  The kits redacted "sensitive" information, including some of the authentication methods and the license enforcement (er, compliance assistance) code.  What was sold as a "source kit" (media, under license) was, nonetheless considered a trade secret with all the markings. 

I had a complete copy of the master source pack in Marlborough during the Aquarius development/debug time; I know I put backup tape of that into the CHM.  That has the CMS library which would go back to at least V1.  (That would be c.a. 1987-9.)  But the master pack contains only the VMS OS & some tightly coupled products (e.g. rms).  The languages were elsewhere, as was the workstation software.