Compton is a compositor for X, and a fork of xcompmgr-dana.
Used for compositing for window managers that do not composite windows themselves, like i3.
Website:
https://github.com/chjj/compton
Tarball:
https://github.com/chjj/compton/archive/master.tar.gz
Open Source:
MIT (or very similar)
I rejected this a while back when evaluating it for i3 (there was no task on the matter, this was done off-Phab) because it hasn't seen a release since 2013 and even that was a beta. It is also infrequently contributed to (last commit was September), so quite frankly it raised questions for me on the longevity of the project. I hold the same opinion on sway, before anyone asks, specifically in regards to beta releases, not the active contributing to sway.