SilverStripe

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Portal CMS

Joomla is a free and open-source content management system written in PHP. The CMS is built entirely by volunteers from all over the world and has a strong community that provide educational resources, and extensions. 

Django CMS is a free and open-source content management system build on the Python web framework Django. With Django CMS, you can create your own website or blog in a matter of minutes which is easy to maintain far into the future. If you are a developer utilizing the Django framework you can integrate Django CMS into an exiting Django application and take advantage of it's publishing and editing features.

CMS Made Simple is a free and open-source content management system that offers an easy to use interface for end users, while maintaining a powerful backend for developers. CMS Made Simple is written in PHP and got an extensive API and custom modules. The CMS also utilize the Smarty templating engine that can be used to customize sites with HTML, CSS and PHP.

PyroCMS is a free and open-source Content Management System written in PHP on top the web development framework Laravel.

Backdrop is a full-featured content management system written in PHP. The Backdrop CMS allows non-technical users to manage a wide variety of content. It can be used to create all kinds of websites including blogs, image galleries, social networks, intranets, and more.

Craft CMS is a flexible, user-friendly CMS for creating custom digital experiences on the web and beyond. Craft is designed from the ground up to empoer the entire creative process. From the user-friendly interface to the completely customizable back end, everything you interact with is designed to just make sense. With Craft your content comes first. No more trying to make your content work within the confines of the CMS.