Open Source Content Management Software
Netlify CMS
Netlify CMS is a static site generator that is based on client-side JavaScript with a reusable APIs and prebuilt Markup. Simply pull in Netlify CMS to /admin of you site and you have an SPA (Single Page Application) admin panel that can edit content stored in a Git repository. Serving applications like this, the JAMstack way, improves performance, lowers cost of scaling and provides for a better development experience.
Mura
The Mura CMS platform makes it easier & faster to build and update websites. The content management system was created to free content managers from distraction of multiple tools, the worry of steep learning curves, and a clear need to tell the right story, to the right audience, at the right time. Mura is loved by content managers, content contributors, marketers and developers alike.
Exponent CMS
Exponent CMS is a notable free and open source content management system that contains its own independent modular software framework of enterprise level.
MASA CMS
MASA CMS is an Enterprise Content Management platform based on open source technology. MASA CMS is a fork of the last open source version of the popular content management system Mura. With MASA CMS you can quickly and efficiently deliver personalised websites and mobile applications. The content management system can easily be installed on-premise or your favorite cloud hosting provider like AWS, Azure, DigialOcean, Linode and many others.
WonderCMS
WonderCMS is the smallest flat file content management system. The CMS is built with PHP and has been developed since 2008. No initial configuration required to setup the WonderCMS, the installation is straight forward and simply requires you to unzip and upload 5 files.All data within WonderCMS is structured as JSON format and the flat file nature of the content management system also allow you to migrate hosts easily by transfering files across, no database migration required.
Bludit
Bludit is a content management system that allow you to build your own website or blog in seconds, it's completely free and open source. Markdown support. The flat file architecture of Bludit makes your websites extremely fast, while still allow you and your team to manage content the way you would in other popular content management systems like WordPress, Joomla and Drupal. Without relying on databases like MySQL or complicated DevOps workflows.
Quanta CMS
Quanta is a free, open source Content Management Framework thought for programmers and used for the creation of new-generation websites and applications.
Strapi
Strapi is a free and open source headless CMS developed with JavaScript for Node.js. The software makes it really simple to generate REST and GraphQL APIs. Simply create your database schema and relationships in the Strapi admin panel UI, and Strapi will auto-generate API endpoints to represent the data structures provided. Strapi comes packed with features you come to expect from normal CMS's such as authentication, authorization, content management and a media library. The software can be used for free and can be self-hosted on any server and platform. Extra enterpise functionallity is currently being developed, and will be sold at cost.
OpenCMS
OpenCMS is based on Java and XML technology that allows you to build highly customizable and interactive websites and portals. The open-source content management system includes a WYSIWYG editor and fully-featured Template Engine which is fully compliant with W3C standards.