The tarball in this directory contains the source code to Ultrix-11 3.1.
This was donated by Steven Schultz who says:

I have the Ultrix-11 source tape that DEC gave/donated to UCB. Keith
Bostic sent me a copy years ago saying "2.xBSD can use whatever it
likes". I've not done much with it since 2.10 and later is quite a
bit more advanced than Ultrix-11 in most areas (and I never liked the
Sys-III/Sys-V features that DEC cobbled on).

Be warned: it's NOT a 'self regenerating' capable kit. DEC apparently
didn't distribute 'source kits' that were complete enough to do that.

Steven

Here are the top few paragraphs from /src/SRCKIT.README:


ULTRIX-11 Version 3.1 Source Kit

The ULTRIX-11 Version 3.1 source kit contains the directories and
files from which the ULTRIX-11 Version 3.1 binary system was built.
These source directories and files are intended for reference only.

To build an ULTRIX-11 Version 3.1 system from these sources, you
already must be running an ULTRIX-11 Version 3.1 binary system.
Then, you can install this source kit on top of your ULTRIX-11
Version 3.1 binary system.