Discourse Alternatives

NodeBB is an open source forum software powered by Node.js and supports either Redis, MongoDB, or a PostgreSQL database. With NodeBB you can self-host communities with instant interactions and real-time notifications powered with the help of web sockets. Thousands of organizations have also stared their communites with NodeBB SaaS product, free from self-service and maintinance.

A free and open-source modern forum software written in PHP. With Flarum you can eaisly setup your own discussion froum and host it online.

Simple Machines Forum or SMF in short is a free and open-source forum software. SMF can be used to build your own online community that you self-host on a host of your choice. Simple Machines Forum comes packed with features for customization, extension and management of your community. The template engine puts you in control of the design of your community. The plugin architecture makes it easy to extend and provide further feautres though third-party built packages. 

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.

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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.

Disqus is a Comment-as-a-Service provider that makes it easy to add comments to any web property. It's one of the most popular comment plugins on the market today. With Disqus, publisher can bring their content to life, fuel colorful discussions, efficiently moderate comments, and build engaged communities. The plugin takes only a matter of minutes to setup and is as easy as installing a WordPress plugin or adding a code snippet to your website.

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.