Unfortunately, I'm not sure archive.org has a clearly delineating way to make it easy to find source code. Many web pages embody some source code as well, but this isn't easy to find and decode.
And of course, there isn't really anything like git to manage the code.
http://minnie.tuhs.org/pipermail/tuhs/2016-February/006622.h...
With the link:
http://www.tuhs.org/Archive/PDP-11/Distributions/research/Mc...
From the Readme:
The structure of the kernel source code is very similar to that of the 1st Edition Unix scan at
http://www.tuhs.org/Archive/PDP-11/Distributions/research/Dennis_v1/PreliminaryUnixImplementationDocument_Jun72.pdf
Here is what I can glean from the files:
01-s1.pdf contains the kernel source divided into sections S1 to S9
02-hw.pdf has hardware details of the PDP-7
03-scope.pdf has information about the PDP-7 scope
04-cas.pdf seems to be a user-mode program that uses the PDP-7 scope
05-1-4.pdf user-mode programs: adm, ald, apr, as
06-5-12.pdf user-mode programs: bl, bc, bi, cat, check, chown, chmod, cp, chrm
07-13-19.pdf user-mode programs: db, dmabs, ds, dsksav, dskres, dskio, dsw, init
08-rest.pdf user-mode programs: ed. Also at the beginning some B code (?)