Yes, JBoss Remoting3 is active and is supported by Red Hat as part of our application server.
For now, we don't have a documentation available yet, but you can check the testsuite if you need a working example.
Thanks for your reply. It's good to know that the project is supported. Regards.
I would add that Remoting 2 will be around for a while, as well. It's not under active development, but it ships with the supported product Enterprise Application Platform 5 (based on Application Server 5), which is contractually guaranteed to be supported for several more years. We won't be adding any new features, but we will continue to do bug fixes as necessary.