"A Quarter Century of UNIX" says:
And in Salus later book, The Daemon, the Gnu, and the Penguin (which I
published for him), he quotes Allman as using 4th edition at Berkeley.
Allman also told me (for my BSD history book in progress), that when he
got involved INGRES was running on 5th Edition and he helped with the
transition to 6th Edition.
Also McKusick's 1985 article "A BERKELEY ODYSSEY: Ten years of BSD
history" says the version 4 tape was delivered in Jan. 1974 (and used on
PDP 11/45) and INGRES was running the newly-available Version 5 of Unix
in the spring of 1974 (on PDP 11/40).
(Following from my book...)
The University of California --- via the
San Francisco Medical School Campus --- was recently
licensed by Western Electric to use Unix. (Fortunately, the
licenses from Western Electric were per-organization rather than
per-computer.)
So Fabry was able to get started with Unix much more quickly than anyone
would have imagined.\cite{fabry2}
%
% NOTE: here is the license for it: archives/1970s/UC_License_4thEd.pdf
% effective Dec. 1, 1973, licensee was the Regents of the Univ.
% NOTE: it says for the location of School of Medicine
% signed on Jan. 7 and 16, 1974
% 2.01
The license allowed use solely for academic and educational purposes.
% 4.05
In addition, the University was prohibited from sharing the software
--- including its methods or concepts --- to anyone other than the
University employees or students.
% NOTE: no version of Unix is mentioned in the license