Wikipedia
XenForo
XenForo is a commercial Internet forum software package written in the PHP programming language using the Zend Framework. The software is developed by former vBulletin lead developers Kier Darby and Mike Sullivan. The first public beta release of XenForo was released in October 2010. XenForo 1.0.0 Stable was released on March 8, 2011. XenForo has several SEO features built in.
On November 12, 2014, Chris Deeming officially joined the development team. One of his products Xen Media Gallery, now XenForo Media Gallery, joined the XenForo family of products.