[cat199]

agree - possibly any of the BSD's might be a good follow up for 'advanced' study since the codebase & kernel structures have a direct lineage. Maybe doing the 'base' course on like 4.2BSD which is still smaller and close to v7 might make sense

[beefhash]

4.4BSD-Lite2 is the earliest they could do without risking some legal issues[1].

[1] https://virtuallyfun.com/wordpress/2018/11/26/why-bsd-os-is-...