https://github.com/larsbrinkhoff/its-presentation -
https://github.com/larsbrinkhoff/oscilliscious Vector graphics audio oscilloscope library.
https://github.com/larsbrinkhoff/emacs-history

This repository contains a port of the "Ritchie C compiler" to the TI990 series processors, in particular the 9995 and 99105 chips. The port is currently fairly complete; only floating point operations remain unported. Other tool chain components (assembler, linker, etc.) are also provided.

The long term goal is to run ancient unix on these chips. As a first stepping stone on that journey, a port of the original 1983 version of the Xinu system has already been completed. The source for that is also in this repository.

Announced on TUHS mailing list https://minnie.tuhs.org/pipermail/tuhs/2021-February/023225.html

Killed by Google is the Google graveyard; a free and open source list of discontinued Google services, products, devices, and apps. We aim to be a source of factual information about the history surrounding Google's dead projects.

Hyper-linked and cross referenced rendition of the sources, much like doxygen or lxr does it. The desired features were:

cover boot, kernel, networking, library and user level code
cover C, assembler and other relevant languages with syntax highlighting
provide 'what is used where' information, over the whole system
provide hyperlinks for a fast code path analysis, especially across the user,library,kernel interfaces
support to follow the execution logic of a system call starting from user code, through the library layer, through the kernel interface, to the kernel code by just following hyperlinks.

Links to archives for the Bell System Technical Journal, the IBM Journal of Research and Development, DEC Technical Journal, the Hewlett--Packard Journal, and the Intel
Technology Journal.

The long term goal of the Software Heritage initiative is to collect all publicly available software in source code form together with its development history, replicate it massively to ensure its preservation, and share it with everyone who needs it. The Software Heritage archive is growing over time as we crawl new source code from software projects and development forges.

Brief description of a failed attempt to install the virtual AGC
from https://www.ibiblio.org/apollo/ on a Raspberry π 4 running Raspian.

So you've written a UNIX utility, library, or driver—or have started writing one—and you want to document your work in a manual. What happens next?
Practical UNIX Manuals: mdoc is a guide for writing portable and maintainable UNIX manuals (manpages) in the mdoc language.
Why mdoc? Formatters for the language are available by default on all modern UNIX installations and may be downloaded for non-UNIX systems. Furthermore, mdoc annotates content semantically, not presentationally, producing consistent manpages across systems. For an analysis of mdoc and competing formats, refer to Fixing on a Standard Language for UNIX Manuals, published in the USENIX magazine.
I also feature the History of UNIX Manpages http://manpages.bsd.lv/history.html , which chronicles the development of manpages from the 1960s to the present day.

Overview of old unix versions which can be run on simulated (or real) pdp-11 computers.
The UNIX-HATERS Handbook, a review on https://athornton.dreamwidth.org/14272.html is also worth reading.

Guides how to install or run older UNIX versions in simh.
Also the UNIX Programmer's manual of V1-V6. V1-V6 are available as nroff output converted to html. V4-V6 are also available as troff'ed PDFs.
The site also has information about Plan 9 and pdp-6/pdp-10.