If you have been keep tracking the open source development, you should have come across a popular name (YaBB), an open source forum board developed in Perl language, which can be a server resource hungry due to the nature of Perl language, while Perl remain a very useful language in the Unix world as system (server side utilities) scripting language, recent development of application programming language has much more spot light shining on on PHP / MySQL, that has led to a new born of Simple Machines Forum, a new successor of popular YaBB with a PHP / MySQL flavor.
Simple Machines Forum, or better known as SMF forum board, is built with a solid ground of user input and years of contribution from the past YaBB community. There are many free PHP forum board available, there are more popular choices than SMF such as phpBB, there are also free PHP forum boards that is yet to match the SMF.
The new SMF is not only stable, it is scalable, fast and require much less server resource thanks to the experience gain from the YaBB. if you are looking for a robust free PHP forum board for your large community, SMF is definitely a choice you should consider.
We have prepare some of the important documentations to get SMF running in your cpanel hosting account, feel free to go through the tutorials and setup a forum board to test out the power of SMF on your own.