Firepad - Open source collaborative code and text editing that relies on Firebase for real-time data...
DokuWiki - DokuWiki is a simple to use and highly versatile Open Source wiki software that doesn't require a database.
CryptPad - CryptPad is a collaborative office suite that is end-to-end encrypted and open-source.
Wiki.js - An open source, modern and powerful wiki app built on Node.js, Git, and Markdown.
eduPad - Real-time collaborative text-editor. No account required. Edits highlighted in authors color.
TiddlyWiki - a non-linear personal web notebook