Outline : Team wiki, documentation, meeting notes, playbooks, onboarding, work logs, brainstorming, & more…
WikkaWiki : WikkaWiki is a flexible, standards-compliant and lightweight wiki engine written in PHP, which uses MySQL to store pages.
Docusaurus : Easy to Maintain Open Source Documentation Websites
Mailtrain : Mailtrain is a self hosted newsletter application built on Node.js (v5+) and MySQL (v5.5+ or MariaDB). Mailtrain supports subscriber list management, ...
Documize is an open source modern, lightweight and comprehensive alternative to Confluence.
It's built with Golang + EmberJS and compiled down to a single executable binary for Linux, Windows and macOS.