All of Unix history now on github "covering the period from its inception in 1972 as a five thousand line kernel, to 2015 as a widely-used 26 million line system. The repository contains 659 thousand commits and 2306 merges, created by synthesizing 24 snapshots of systems developed at Bell Labs, Berkeley University, and the 386BSD team, two legacy repositories, and the modern repository of the open source FreeBSD system."
Quite some analysis is presented on this page, and git allows further digging: "running git blame on the kernel's pipe.c file will show lines written by Ken Thompson in 1974, 1975, and 1979, and by Bill Joy in 1980"
Some of the earliest code was recovered by OCRing printouts!
"The data set can be used for empirical research in software engineering, information systems, and software archeology."
It's legit, too: "Although Unix was initially distributed with relatively restrictive licenses, the most significant parts of its early development have been released by one of its right-holders (Caldera International) under a liberal license."
via the discussion athttps://news.ycombinator.com/item?id=9588175
where we find this comment:
"""I took a university course on Unix internals in 1988. The lecturer started by announcing "this is the last year that we will teach this course as Unix is now very out of date and is being left further behind every year". It turned out to be the best course I ever took.