esoTalk

esoTalk is a free, open-source forum software package built with PHP and MySQL.

Directly

Directly provides on-demand customer service apps.

Discourse is an open source discussion platform built for the next decade of the Internet.

FUDforum is a free and open source Internet forum software

Forumbee offers community forums for discussions, feedback and Q&A.

Build a community and a business on mobile

MyBB is a discussion board software that runs on PHP and MySQL

SocialGO enables users to create custom social networking websites.

TinyBB is an open-source forum software written in PHP, MySQL, and HTML.

Build an engaging community forum using Vanilla’s modern cloud forum software.

Intuitive. Social. Engaging. Fast. XenForo brings a fresh outlook to forum software.

Communities at Zimbra.

jforum is a Java-based discussion board software.