Flarum is the simple open source forum software that makes online discussion fun. You can use Flarum to easily set up a discussion forum for your website. Flarum looks and feels great out of the box. The user interface is streamlined so you can spend less time clicking and more time talking.
There is a Floating Composer, you can read while you write. Flarum’s reply form slides up from the bottom of the page, so you can scroll up to read posts – and even visit other discussions – while you draft your reply. This is forum software for humans. Flarum is carefully designed to be consistent and intuitive across platforms, out-of-the-box.
Requirements: PHP and MYSQL
Website : http://flarum.org/
License: Creative Commons 3.0 License