Open Source Software for Self-Hosted
TYPO3
TYPO3 is a free and open-source content management system written in PHP. The CMS is released under the GNU General Public License which makes it free to use for commerical and non-commercial projects alike. TYPO3 can run in most hosting environements and provides an easy way for people to write, manage and publish content online.
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.
Plone CMS
Plone CMS is a free and open source content management system written in Python. The CMS is built on top of the Zope application server, a free and open source web application server written in the object-oriented programming language Python. The significant strength of Plone is its flexibility, allowing users to manage the lifecycle of their workflow, from creation to publication and storage, with version control, content locking, and digital asset and document management. Plone has an active, thriving open source community that holds annual conferences, regional symposia, and many sprints all over the world. Which means that anyone if free to join and improve the codebase
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.
DatoCMS
Connect DatoCMS to your favorite site generator, build the perfect backend and deploy anywhere you like.
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.
Wagtail
Wagtail is a free and open-source CMS built on-top of Django and Python. The CMS is built by developers and for developers and provides a configuration-less solution to content management. Wagtail plays nicely with your existing tech, especially if that stack utilze Python and the Django web framework. Wagtail can be installed as a package in existing Django application and extends the Django Admin to be more suited for content management.
Kotti CMS
Kotti is a high-level, Pythonic web application framework. It includes an extensible Content Management System called the Kotti CMS, offering all the features you would expect from a modern CMS. Kotti is built on top of a number of best-of-breed software components, notably Pyramid, SQLAlchemy, and Twitter Bootstrap.