I've been trying, on and off, for nearly six months to get two versions of ColdFusion, CF 8 and CF 9, running in a MultiServer install of CF with JRun on my Mac. I've read all of the documentation that is available, as well as a good number of blog posts, but I always seem to get stuck at the point of deploying my CF9 EAR into my existing copy of JRun (which was installed during the MultiServer install of CF8). Everything I've read suggests that auto-deploy should work - you just copy your exploded EAR into a folder under JRun/servers/ and JRun will deploy CF9 for you. Well, for whatever reason, that simply does not work with my setup. I also tried to manually deploy (in spite of there seeming to be zero documentation on how to do that), but still could not get my instance of CF9 to start up in JRun.
After walking through all of the steps yet again yesterday, and coming up with the same result, I asked someone who in my mind is the most knowledgeable person about this topic, particularly when it comes to OS X, Sean Corfield. We discussed the steps I had taken, and he suggested that auto-deploy with JRun can be problematic. He then suggested a solution that worked perfectly for me, so I'm going to share it with you here.