Software
Flextype
Flextype is super fast headless content management system with an elegant architecture and built-in smart cache.
Mixcore CMS
Mixcore CMS is an Open Source Enterprise ASP.NET Core / Dotnet Core CMS for building amazing digital experiences. It's made by a dedicated community. Anyone can use it, and it will always be free.
CouchCMS
With no knowledge of PHP required at all you can make any static web-page editable by your clients.
Subrion
Subrion is a PHP/MySQL based CMS & framework that allows you to build websites for any purpose. Yes, from blog to corporate mega portal.
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.
TourCMS
TourCMS is a web based reservation system for tour operators and travel agencies, TourCMS - Tour operator reservation system and website CMS
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.