Vanilla Forums - Build an engaging community forum using Vanilla's modern cloud forum software.
Homeland - Homeland is an open-source community/forum system for business use.
Discourse - Discourse is an open source discussion platform built for the next decade of the Internet.
PunBB - PunBB is a fast and lightweight PHP-powered discussion board.
Directly - Directly provides on-demand customer service apps.
XenForo - Intuitive. Social. Engaging. Fast. XenForo brings a fresh outlook to forum software.