Today I am open sourcing my tiny, zero dependency Wayland compositor Nyctal: https://github.com/s-rah/nyctal
(or about 3000 lines of code you would have to write anyway....)
Nyctal is far from "finished" - and you probably wouldn't want to deploy it. There is plenty of bugs to squash, and features/extensions I really want to add.
But it has reached a state where doing those things incrementally on a public code base is a better choice than to continue hacking away in private.