Open Source Content Management Software
ExpressionEngine
ExpressionEngine is a flexible, feature-rich content management platform that empowers hundreds of thousands of individuals and organizations around the world to easily manage their web site. ExpressionEngine has a large community of developers that make add-ons that extend the system capability. With ExpressionEngine add-ons, no matter the task, you'll have a solution.
WordPress
WordPress powers roughly 30% of all web pages online. It's a free and open source CMS designed and developed for self-hosted publishing by Automattic, Inc. The software is written in PHP and utilize either MySQL or MariaDB as a database, and is compatible with most web hosts. Wordpress includes a plugin architecture and a templating system that can be used to extend and customize your website. These are commonly known as WordPress plugins and WordPress themes and make up a whole open source and commercial eco-system where anyone is free to create products for the platform.
CMS Made Simple
CMS Made Simple is a free and open-source content management system that offers an easy to use interface for end users, while maintaining a powerful backend for developers. CMS Made Simple is written in PHP and got an extensive API and custom modules. The CMS also utilize the Smarty templating engine that can be used to customize sites with HTML, CSS and PHP.
PyroCMS
PyroCMS is a free and open-source Content Management System written in PHP on top the web development framework Laravel.
Drupal
Drupal is a free and open-source CMS written in PHP. Drupal is used for creating website for businesses, political parties and governments. The CMS currently powers 2% of all websites on the internet.
Pangea CMS
Pangea CMS is a powerful content management system designed for journalists. Pangea CMS provides a platform for quality and balanced journalism in 57 languages across 200 countries and territories around the world.
Batflat
Batflat is fast, database-less CMS written in PHP. Batflat weighs in on 1024 kilobytes and it has all features you have come to enjoy from other content management systems like WordPress. You can also download or create your own extensions for Batflat, allowing you to build features on top of the core and create unique experiences for the end-user.
Statamic
Statamic is a flat file based content management system written in PHP. With Statamic you can build better and faster websites that are easy to manage. Statamic features over 40 field types, drag & drop navigation builder, revision and content history, inline content editing, asset management, plugin architecture and real-time collaboration that makes content management a breeze.
Superdesk
Superdesk is a state-of-the-art digital newsroom system that combines headless CMS functionality with powerful workflow features for an end-to-end news creation, production, curation and distribution platform. With Superdesk you can create and distribute content to any platform. All within a web-based dashboard that share many similarities with a regular newsroom, while providing remote-friendly workflows that will make journalist feel right at home.
Saaze
An all-inclusive, flat-file CMS for simple and fast content management. While regular content management systems like WordPress are great, the complexity of running sush a site can easily become a burden. They also have a larger attack vector due to popularity and the fact that they utilize a relation database mangement system to serve and manage the content. Saaze is fundamentally different, the flat-file architecture of Saaze makes hosting content for the web easy to manage, secure and fast to load.