Stonly Knowledge Base - Interactive knowledge bases and help-centers
MediaWiki - MediaWiki is a free software wiki package written in PHP, originally for use on Wikipedia.
Free Knowledge Base by Dashly - Optimize your customer support with Knowledge Base by Dashly
TiddlyWiki - a non-linear personal web notebook
Intercom - Intercom is a customer relationship management and messaging tool for web businesses. Build relationships with users to create loyal customers.
Confluence - Confluence is content collaboration software that changes how modern teams work