OpenCMS

vs

ImpressCMS

Sitecore A/S has produced the Sitecore content management system since 1999.

MODX is a free, open source content management system and digital experience platform. The CMS gives you full control over your creative, editorial vision and the experience you deliver. MODX is written in the programming language PHP and supports both MySQL and Microsoft SQL Server databases. The CMS is openly developed and released under the GPL license, and allows contribution.

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. 

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

WordPress powers roughly 30% of all web pages online. It's a free and open source CMS designed and developed for self-hosted publishing by Automattic, Inc. The software is written in PHP and utilize either MySQL or MariaDB as a database, and is compatible with most web hosts. Wordpress includes a plugin architecture and a templating system that can be used to extend and customize your website. These are commonly known as WordPress plugins and WordPress themes and make up a whole open source and commercial eco-system where anyone is free to create products for the platform. 

Drupal is a free and open-source CMS written in PHP. Drupal is used for creating website for businesses, political parties and governments. The CMS currently powers 2% of all websites on the internet.