Kunena is the leading Joomla forum component. Downloaded more than 8M times in 11 years, Kunena is the only forum/discussion solution for Joomla that is community driven - true open source - public self-help forums, GitHub and documentation Wiki.
The most recent stable release, recommended for production websites running J! 4.1/4.2, is Kunena 6.0.2
For websites running J! 3.10 there is Kunena 5....