Open Source Forums / Bulletin Boards

phpBB

phpBB is free and open source forum software that is easy to use, powerful, and highly customisable.

Simple Machines Forum — SMF

Simple Machines Forum — SMF in short — is a free, professional grade software package that allows you to set up your own online community within minutes.

Phorum

Phorum is open source forum software with a penchant for speed. Phorum's very flexible hook and module system can satisfy every web master's needs.

bbPress

bbPress is forum software with a twist from the creators of WordPress.

FluxBB

FluxBB is a fast, light, user-friendly forum application for your website.
FluxBB is designed as a lighter, faster alternative to some of the traditional feature heavy forum applications. It is easy to use and has a proven track record of stability and security making it an ideal choice of forum for your website.

Kaibb

KaiBB, a free and open source bulletin board software powered by php and mysq

miniBB

miniBB is a free standalone open source program for building your own Internet forum. It's developed with just a purpose of posting and getting messages, answering questions, spreading opinions, providing support, and other kind of the online public communication between website visitors and maintainers, performed quickly and effectively

MyBB

The official homepage for MyBB, a free PHP and MySQL based discussion system

MyLittleForum

my little forum is a simple PHP and MySQL based internet forum that displays the messages in classical threaded view (tree structure). It is Open Source licensed under the GNU General Public License.

PunBB

PunBB is a fast and lightweight PHP-powered discussion board. It is released under the GNU General Public License

XMBForum

XMBForum.com, home of eXtreme Message Board and it's community. XMB is a lightweight PHP forum software with all the features you need to support a growing community.

Vanilla Forums

Vanilla Forums are open-source, standards-compliant, customizable discussion forums.

UseBB

UseBB.net is the official website of UseBB 1, a mature, light and Open Source PHP 4 and MySQL based forum package, distributed freely under the GPL license.