We've been using jbossmq and csil. The implementation has been successful in production for 6 years, but I'm wondering if something better is available.
One issue is jbossmq's thread per client model, and scheduled end of life. Another is csil's lack of support for JBossMessaging, which is the latest JMS implementation from JBoss.
You should look at an ActiveMQ backend with NMS clients. I've had no problems with it. I can't vouch for it though because the production system I am using it in is not high volume.
I recommend you take a look at IKVM. It is a compiler that generates .NET assemblies from java byte code (jars). We have had good success, stability and performance using native JBoss assemblies created by IKVM and we've implemented the usual client side protocol (RMI, JMS, EJB) although, not actually the new JBossMessaging. At any rate, implementing this approach, you can pick which ever remoting protocol suits you best with less worries about compatibility,
//Nicholas
I am author of jni4net, open source intraprocess bridge between JVM and CLR. It's build on top of JNI and PInvoke. No C/C++ code needed. I hope it will help you.