Booru notes...
me said:
I want to set up a booru, and I don't want to make something from scratch, but which one do I pick?!?
Shimmie2 (source)
The base for this booru's source code (which has its own source here!)
e621ng (source)
https://e621.net/wiki_pages/11244 said:
e621's source code is a heavily modified fork of the Danbooru code. It is a Ruby on Rails application. It has been made officially Open Source on March 5th 2020.
Szurubooru (source)
https://github.com/rr-/szurubooru said:
Szurubooru is an image board engine inspired by services such as Danbooru, Gelbooru and Moebooru dedicated for small and medium communities.
Gelbooru
Currently does not seem to be open source, and doesn't look too promising from this discussion on open sourcing it.