Is there any open source forum software that supports threading and does not require users to register for an account before posting? This is somewhat similar to anonymous imageboards, but with threading, no images, and optional user registration.
Probably most forum software have such an option, you just need to set it correctly.
- phpBB can do that. You just need to set (in Forum Permissions) Standard Access for the Guest Group.
- NodeBB is a more modern option. See the posting without registration in the Testing Ground forum on their demo site https://try.nodebb.org/