386bsd - First open source BSD operating system, by William and Lynne Jolitz.
All release's are currently inconsistent due to media failures and composing from undated partial copies as I'm able to extract them from drives, tapes, and floppies.
Basically, working through boxes of decades old stuff/notes. 0.1/1.0 are self-compiling on small memory systems (<32MB), and virtual machines like QEMU and Virtual Box.
So the branches are idiosyncratic WRT time, and 0.1/1.0 are the most useful at the moment (2.0's got the most lapses at the moment).
After it all gets sorted out, look for ".x" branch which will deal with the "going forward" stuff (from a second box!).