Developed by devhub.io
Vanilla is a powerfully simple discussion forum you can easily customize to make as unique as your community.
The Laravel.io Community Portal
The best Rails forums engine ever.
A Django forum engine for building powerful community driven websites.
Source of PHPMap
A modern alternative to ancient forum CMSes like vBulletin and PHPBB in Python on Django. (Alpha stage.) (NB: dotCloud have since removed their free Sandbox tier.)
Discourse-like forums, in Go.
A bulletin board and content management solution
:hourglass: Free, open-source and self-hosted forum software written on top of the Laravel framework.
Bitnami Docker Image for Discourse
Threema Gateway implementation for XenForo, offers two-step-authentication (or two-factor-authentication 2FA) for users
Como Fazer Perguntas de Maneira Inteligente: uma versão traduzida e atualizada do original de Eric Steven Raymond