I want to launch an app at login but have it running as a specific user. Here's the use case:
I turn on my Mac and login in as Ben. In the background iTunes is launched for Bill. Ben can launch his own instance of iTunes and access Bills songs via iTunes sharing. Ben doesn't care have access to Bills instance of iTunes. All other iTunes on the local network can also access Bills shared iTunes library.
Please don't suggest iTunes specific solutions (e.g. Home Sharing) as I also want to run other apps in a similar fashion.
Is this possible?