Stonly Knowledge Base - Interactive knowledge bases and help-centers
DokuWiki - DokuWiki is a simple to use and highly versatile Open Source wiki software that doesn't require a database.
Free Knowledge Base by Dashly - Optimize your customer support with Knowledge Base by Dashly
Wiki.js - An open source, modern and powerful wiki app built on Node.js, Git, and Markdown.
Intercom - Intercom is a customer relationship management and messaging tool for web businesses. Build relationships with users to create loyal customers.
TiddlyWiki - a non-linear personal web notebook