What is the best free, or GNU licensed JMS server. We want something that is easy to install and will "just work" without too much intervention on our part.
We are open to other non JMS and even non Java messing solutions, but there would have to be a compelling reason to use a different non Java based solution with our Java applications. It should also be lightweight, SOAP for example does not perform well when you are dealing with millions of messages.
Background
We have already had one foray into doing messaging using Active MQ. It turned out to be great except for the fact that Active MQ would mysteriously die every few days with no clues as to what went wrong. We were probably averaging about 1-2 million messages per day. We ended up canning the solution because we need something that is not going to fall over every other night when we are in bed.