draw² was my project submission in Spring 2013 for 4002-546 Web Client Server Programming at Rochester Institute of Technology. You can view the project requirements via 546_PROJECT.pdf. It uses Meteor (including MongoDB) as the platform and D3.js for drawing generation. Users (after registering) can create private drawing rooms as well as chat with other users. I've open-sourced draw² for future students to reference as an example (and who knows, perhaps someone will pick it up and develop further).
Since draw² was created using a now-deprecated version of Meteor and Meteorite, you'll have to follow these specific instructions to get it running.
sudo -H npm install -g meteorite
sudo mrt
http://draw-squared.meteor.com/
Released under the MIT license