DokuWiki

DokuWiki is a wiki engine that stores every page as a plain text file in a folder, so a site runs on any PHP host with no database to install or maintain. It adds page history, revision diffs, access control lists, backlinks, and plugins for media galleries, syntax highlighting, and other extras.

Small teams use it for internal handbooks, runbooks, and meeting notes that should stay readable and greppable without a vendor account.

The service can it on your own server, where the content can be versioned with Git and no per-user fee applies to basic wiki features.