Cells
Pydio Cells is the Document Sharing, Management, and Collaboration platform.
Wikijs
Wikijs is a powerful open-source wiki app built on Node.js, Git and Markdown.
Outline
Outline is a fast wiki and knowledge base for growing teams - an alternative to Google Docs.
BookStack
BookStack is a platform to create documentation/wiki content built with PHP & Laravel.
Documize
Free Knowledge Management Software
DocuSeal
Open source, tool to streamline document filling and signing. Create custom PDF forms to complete and sign with an easy-to-use online tool.
Answer
An open-source knowledge-based community software. You can use it quickly to build Q&A community for your products, customers, teams, and more.