Hazelcast

If you're looking for a top-notch, open-source clustering data distribution platform for Java, then look no further than Hazelcast. This platform offers a scalable solution for many different use cases, including caching data, sharing data or state among multiple servers (such as web session sharing), partitioning in-memory data, clustering your application, distributing workload onto multiple servers, taking advantage of parallel processing, and providing fail-safe data management.

One of the best things about Hazelcast is that it is purely Java-based, which means that JVMs running Hazelcast will dynamically cluster. Additionally, Hazelcast uses TCP/IP with Java NIO beauty for communication among cluster members, and can be configured to use multicast for discovery (or TCP/IP for environments where multicast is not available or preferred).

Another great feature of Hazelcast is its default configuration, which includes one backup, ensuring that no data is lost if one node fails. It's as simple as using java.util.{Queue, Set, List, Map}: just add the hazelcast.jar into your classpath and start coding.

Overall, Hazelcast is an excellent choice for those looking for a reliable, open-source clustering data distribution platform for Java. Best of all, Hazelcast is licensed and released under the terms of the Apache License, making it easy for developers to use and expand upon.