Gauntlet is a project mainly written in JAVASCRIPT and JAVA, it's free.
Building the playn example (maven 3 required):
cd gauntletplayn
mvn install
Running the example in Java (from IDEA):
run GauntletGameJava class
Running the example in JS:
mvn clean install mvn test -Dtest-html
open http://localhost:8080/ (and reload)