Firepad : Firepad is an open-source, collaborative code and text editor. It is designed to be embedded inside larger web applications.
NicEdit : WYSIWYG Content Editor, Inline Rich Text Application
Closure Tools : The Closure Compiler, Library, Templates, and Stylesheets help developers create powerful and efficient JavaScript.
HedgeDoc : HedgeDoc (formerly known as CodiMD) is an open-source, web-based, self-hosted, collaborative markdown editor.
You can use it to easily collaborate on ...
EtherPad : Etherpad is an Open Source online editor providing collaborative editing in really real-time powered by Node.js
MobWrite converts forms and web applications into collaborative environments. Create a simple single-user system, add one line of JavaScript, and instantly get a collaborative system.