diffsync: This addon contains a foundation for developing real-time collaborative Vaadin components. Also included is a couple of examples. One of the examples, CollabTextArea, provides a multi-user editable text area and can be used as is.
There’s a tutorial how to use it behind the Source Code link →
If you try it I’d like to know if that actually works. :)
This is an experimental addon, interfaces etc. are subject to change.