Homeland - Homeland is an open-source community/forum system for business use.
Vanilla Forums - Build an engaging community forum using Vanilla's modern cloud forum software.
Discourse - Discourse is an open source discussion platform built for the next decade of the Internet.
Directly - Directly provides on-demand customer service apps.
PunBB - PunBB is a fast and lightweight PHP-powered discussion board.
MyBB - MyBB is a discussion board software that runs on PHP and MySQL