The game uses a modern web browser (Firefox and Chrome have been tested) for the clients and Node.js on the server. A quite recent version of Node.js is required: in particular, Ubuntu 13.10 ships a version that is too old.
To install Node.js on Ubuntu (it should in theory work on any OS where Node.js runs, but it's untested):
sudo apt-add-repository ppa:chris-lea/node.js
sudo apt-get update
sudo apt-get install nodejs
No other steps are needed to build: it's all ready in the release/ directory.
To run the server, change to the `release/server` directory and run `node index.js`. It will run a web server on port 8888. Point the clients at http://yourmachine:8888/client/.