UberMQ 1.0, in beta for several months, has finally been released! UberMQ is an implementation of the JMS topic (pub/sub) API featuring a clean-room architecture, Java NIO for speed and scalability, and all of the robust enterprise-level features you need from a messaging solution. Since it is open-source, it is easy to extend and modify the behavior to suit your project's goals.
Please visit our website at http://www.ubermq.com for more details on the product's design and feature set. Thanks for your support!