Software
Flextype
Flextype is super fast headless content management system with an elegant architecture and built-in smart cache.
LightCMS
Easily Create Fantastic Websites with Highly Customizable Templates & Intuitive Tools for...
CouchCMS
With no knowledge of PHP required at all you can make any static web-page editable by your clients.
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
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.
