Available on GitHub.
A self-hosted “platform as a service”, inspired by Heroku. There are a few ways of using it, but the simplest is the classic “git push to deploy” which was an early defining characteristic of Heroku.
A lot of my projects are hosted using it, on a VPS I operate. It’s a bit of a hassle sometimes, but Heroku is so expensive once you have, say, ten things you want to run all the time.