Discourse is described as 'Open source discussion platform built for the next decade of the Internet. A modern forum, everything's been redesigned to be easy' and is a very popular Forum Software in the social & communications category. There are more than 50 alternatives to Discourse for a variety of platforms, including Web-based, Self-Hosted, SaaS, Linux and Windows apps. The best Discourse alternative is Flarum, which is both free and Open Source. Other great apps like Discourse are phpBB, NodeBB, Vanilla Forum and XenForo.
Flarum is free, open-source forum software with a focus on simplicity. You can use Flarum to easily set up a discussion forum for your website. Flarum is developed openly on GitHub.
Works on more shared-hosting environments, and is more cleanly designed / easy to set up.
Since its creation in 2000, phpBB™ has become the most widely used Open Source forum solution. Like its predecessors, phpBB™ 3.2 “Rhea” has an easy to use administration panel and a user friendly installation process, which allows you to have a forum set up in minutes.
A community forum allows you to engage and retain customers, keeping them interested and up-to-date with your latest product or service.
Vanilla provides a standards-compliant, multi-lingual, theme-able and pluggablecommunity forum software that powers discussion forums on 800,000 sites.
Vanilla only supports open-source for Developers, they discourage use for non-profit or hobbyist purposes over a paid solution.
A compelling community experience. Intuitive. Social. Engaging. Fast. XenForo brings a fresh outlook to forum software.
Simple Machines Forum — SMF in short — is a free, professional grade software package that allows you to set up your own online community within minutes.
Invision Community is a flexible, feature-packed and easy to customize platform that powers some of the biggest and best communities on the web.
MyBB is the free and open source, intuitive, extensible, and incredibly powerful forum software you've been looking for.
bbPress is forum software with a twist from the creators of WordPress. Its focused on web standards, ease of use, ease of integration, and speed. bbPress will try to keep things as small and light as possible while still allowing great add-on feature possibilities.
vBulletin (abbreviated as vB) is a commercial Internet forum software written in PHP using a MySQL database server.
WoltLab Suite (formerly Burning Board) is an enterprise grade CMS built for communities and forums.
Open Social is a purpose-built community engagement platform. Developed on top of a powerful open-source Drupal technology framework, Open Social allows organizations to create a central online hub for their members.
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Its fast lite-weight and easy, works with php and mariadb/mysql