Most likely JackRabbit is relying on the javax.jcr.* classes that are not deployed to JBoss by default. They don't seem to be included in the JackRabit RAR as well. JackRabbit defines this as it's connection-defintion. Since we can't find it, we can't create the connection.
Verify where these classes are supposed to exist in the JackRabbit documentation. There is usually one of two places:
1) The server/lib directory
2) Inside the RAR