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Simple Machines Forum

Create an online community that your customers will love. Vanilla's forum software is used by top brands to engage customers, drive loyalty and reduce support costs. The software is provided free and open-source as a self-hosted solution and can be bought by businesses and enterprises as a managed and hosted solution.

Discourse is an open source internet forum and mailing list software. The application is written with Ember.js and Ruby on Rails, and can be self-hosted in the cloud or on local hardware for free. Discourse also provides managed hosting starting at $100/month, so that you can focus on building a community rather than installing software and managing servers.

One of the world most popular, free, open-source and self-hosted forum software, written in PHP. With phpBB you can create communities that can be hosted with most hosting providers. The software package is built and designed from the ground up to to be extensible and provides customization option through themes and feature extensions through plugins. The extensive database of user-created extensions and styles database, easy of use, and the simple installation process has made phpBB a common choice among self-hosted forums and communities.

LayerBB is a small yet feature rich, free and open-source community software written in PHP. LayerBB enables you to quickly and easily start your own community while providing great flexibility and customisability.

vBulletin is a powerful commercial forum software written in PHP. The software is built to be easily extended through plguins and customized with themes. vBulletin is used to power many of the largest forum, communities and social site across the web. Over 100,000 sites are currenty powered by vBulletin.

bbPress is forum software from the creators of WordPress. With bbPress you can quickly setup a forum for asyncronous discussion and subscriptions for your WordPress-powered site.