Combine this with one of those tiny self-compiling C compilers that were the subject of a few HN articles recently (e.g. https://news.ycombinator.com/item?id=8576068, https://news.ycombinator.com/item?id=8558822) and this could be one of the more interesting minimal self-hosting OSs someone could understand the entirety of in a relatively short amount of time. I like how it supports multiprocessing too, and the entire kernel is <100 pages in the source code PDF.

However, I wish they'd use something other than GAS for the Asm parts... a minimal self-assembling assembler (and a C-subset compiler written in it, to bootstrap the whole thing) would be nice.