Collaborative editor: up to 14 participants can edit a page simultaneously in real-time.
* http://en.wikipedia.org/wiki/MoonEdit

It's easy to install: download a single archive, which contains a binary for the client and a binary for the server. Both run without any install process. The server app runs on any PC and you can pick the port it listens on. 
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CategoryCollaboration, CategorySoftwareTool, CategoryTextEditor