MyBB, is a free and open source forum software, which is developed by the MyBB Group. It is written in PHP and supports MySQL, PostgreSQL and SQLite. Released under the LGPL.
MyBB (originally MyBulletinBoard or MyBBoard), is a free and open source, intuitive, extensible, and incredibly powerful forum software.
MyBB is known to be very customisable with an extremely easy-to-use plugins system (while still powerful), themes & templates make it possible to give the forum the exact style and look you like, anything you don't like can be removed easily.
MyBB has a comprehensive control panel for users and for administrators and wide availability of translations (including right-to-left support).
MyBB released under the LGPL.