In the modern world of business, it is useless to be a creative original thinker unless you can also sell what you create. Management cannot be expected to recognize a good idea unless it is presented to them by a good salesman.
David M. Ogilvy

Simple Machines Forum – SMF – is free, top-quality forum software using PHP and MySQL. It’s a conventional forum with a similar layout and structure to commercial forum packages. Upgrading is particularly simple compared to other web applications – full version upgrades can be done through the package manager of the admin system.

More information is available from the Simple Machines web site.

A note about SMF licensing

SMF is not released under any of the common open-source licences; instead the project team has introduced their own more restrictive licence which prohibits redistribution of the source code without specific permission. Nevertheless it is free to use (including commercial use) and there are no restrictions on making your own modifications or publishing them.

This means in effect that most of the advantages of open source software are maintained – notably peer review and community involvement in development – but forking is not possible. ie. another team cannot produce their own version of the software and develop that independently. Although unlikely, this could conceivably cause problems for users in the future since they are in effect “locked-in” to the current development team.

In short, some open-source purists may prefer to avoid SMF based on it’s licensing but most regular users will have no problems with it.