Free Content Management Software
Anchor CMS
Anchor is a super-simple, lightweight blog system written in PHP. Compressed, Anchor CMS weighs in at just under 250kb making it an extremely light weight content management system. With Anchor CMS, you can manage content in HTML or Markdown, depending on which you prefer. The content management is fully free and open-source and released under the GPL-3.0 License.
Subrion
Subrion is a PHP/MySQL based CMS & framework that allows you to build websites for any purpose. Yes, from blog to corporate mega portal.
GeniXCMS
GeniXCMS is a Simple and Lightweight CMS and Framework. It's PHP Based CMS. Free and Opensource.
Mixcore CMS
Mixcore CMS is an Open Source Enterprise ASP.NET Core / Dotnet Core CMS for building amazing digital experiences. It's made by a dedicated community. Anyone can use it, and it will always be free.
CouchCMS
With no knowledge of PHP required at all you can make any static web-page editable by your clients.
LightCMS
Easily Create Fantastic Websites with Highly Customizable Templates & Intuitive Tools for...
Flextype
Flextype is super fast headless content management system with an elegant architecture and built-in smart cache.
Agility CMS
Agility CMS is a cloud-based content management system for building and managing responsive websites and apps.
Rooftop
Rooftop is a open source and managed, API-only implementation of the WordPress CMS. With Rooftop, developers can harness the power of WordPress and write frontends in any language. Rooftop can be used to build websites, web applications and mobile applications.