Free Software for Self-Hosted
CushyCMS
CushyCMS is a FREE hosted content management system that's actually easy to use, fast to setup and doesn't require programming skills.
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.
FeinCMS
FeinCMS is a bare bones content management system written in Python on-top of the web framework Django. The CMS is built to know nothing about your content, and includes an admin interfaces that can handle content types. It lets you reorder page content blocks using a drag-drop interface, and you can add as many content blocks to a region (sidebar, header, etc) as you want. FeinCMS was built this way to allow for maximum flexibility, where developers, designers and content managers can create a unique site, tailored for their type of content and future patterns.
Flextype
Flextype is super fast headless content management system with an elegant architecture and built-in smart cache.
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.
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.
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.
CppCMS
CppCMS is a free and open-source, high performance web development framework. CppCMS is not a content management system but rather a C++ web framework that has been designed for rapid web application development. Applications built with CppCMS are capable high loads with high request throughput.
SilverStripe
Silverstripe CMS is designed to be simple to learn and easy to use. Whether updating a page or publishing multiple pages on a large scale site. Give access to edit only specific areas of your site. Architected to safeguard your data from malicious activity or data-loss, even while scaling up complex sites.
DatoCMS
Connect DatoCMS to your favorite site generator, build the perfect backend and deploy anywhere you like.