After the successful launch of Meadow, I can confidently push my open-source multiplayer Java platform:
http://fuse.rupy.se/about.html
I will port the Java client when I port Aeon to Fuse, but this platform with C# (Unity), C++ and HTML5 clients is really delivering on the strengths of the Java VM on the serverside (Classloader Hot-Deployment, Parallelism, Concurrency and NIO).