WordPress is a free and open-source content management system written in PHP and paired with a MySQL or MariaDB database. Features include a plugin architecture and a template system, referred to within WordPress as Themes.
Drupal is a free and open-source web content management framework written in PHP and distributed under the GNU General Public License. Drupal provides a back-end framework for at least 2.3% of all websites worldwide – ranging from personal blogs to corporate, political, and government sites.
Ghost is a free and open source blogging platform written in JavaScript, it is designed to simplify the process of online publishing for both individual bloggers and online publications
Joomla is a free and open-source content management system for publishing web content, developed by Open Source Matters, Inc. It is built on a model–view–controller web application framework that can be used independently of the CMS.
Elgg is open source social networking software that provides components for individuals and organizations to create an online social environment. It involves blogging, file sharing, networking, groups and other features