Tina CMS
A fully open-source headless CMS that supports Git and Visual Editing.
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TYPO3
TYPO3 is an enterprise-class, open source CMS, used internationally to build and manage websites of all types, from small sites for non-profits to multilingual enterprise solutions for large corporations.
Vvveb
Powerful and easy to use CMS with page builder to build websites, blogs or ecommerce stores.
VvvebJs
Drag and drop website builder javascript library.
Wagtail CMS
Wagtail is a content management system built on Django. It's focused on user experience, and offers precise control for designers and developers.