esoTalk – Simple, Fast & Modern Forum App
Previously, a post at WRD had shared the 9 well-known and free forum softwares.
Here is a fresh alternative named esoTalk, which focuses on removing the complexity of forum apps with a simple + modern interface and functionality.
It is built with PHP-MySQL, includes the main features a forum would need and has a plugin system for extending it more.
esoTalk is still in the early stages of its development, not as feature-rich as many other alternatives. But, maybe, something simpler is what you are looking for.