Adobe Experience Manager (AEM/CQ) is at its core open source. But you're right in that manner, that they don't promote these projects or help them to grow.

https://sling.apache.org/ - the core

http://jackrabbit.apache.org/jcr/index.html - content repository

https://github.com/Adobe-Marketing-Cloud/htl-spec/blob/maste... - htl/sightly (template language)

Not a fan of Adobe software, but they created the open source text editor Brackets:

http://brackets.io/

They also have a series of high quality open source fonts:

Source Sans Pro: https://github.com/adobe-fonts/source-sans-pro

Source Serif Pro: https://github.com/adobe-fonts/source-serif-pro

Source Code Pro: https://github.com/adobe-fonts/source-code-pro