The only thing that isn't is the very old puppet script that managed the deploy as it was rather bespoke for our setup.
To my own regret I focused far too much on making it an effective platform rather than an easy install, so that bit might feel gnarly but at least the errors are sane and guide you.
The Go API and PostgreSQL schemas: https://github.com/microcosm-cc/microcosm
The Django frontend (the client is nothing but a thin client over the API) https://github.com/microcosm-cc/microweb
The Bootstrap derived theme for the Django fronted https://github.com/microcosm-cc/microweb-bootstrap
And then other miscellaneous things:
The Go HTML sanitizer for user generated content https://github.com/microcosm-cc/bluemonday
Our legal policies for forums on this platform (expensive to produce, but perfectly fitting a forum platform with minimal exposure for the platform owner/admin and minimal but some liability for a forum owner) https://github.com/microcosm-cc/legal
There is also a newer thing, I was (/am?) intending to replace the Django layer with a Go frontend and templating, and then moving the API into this, such that the forum could become a single binary install and thus gain a new lease of life: https://github.com/buro9/microcosm . Once in a while I chip away on that.