I'd like to hear an answer to this one, too. I can't believe that once you start an app, you have to leave it running until you shut down !!!
I sideloaded SysInfo, and didn't start the music player after shutting down. The music player didn't show up in the list of processes. Once I started it, it did show up highlighted and cycled between zero and 1% of CPU. When I paused it, it greyed out, but still occasionally cycled to 1%, so it definitely wasn't off, even when I put the NT to sleep and woke it up. The only way I could find to turn it off, was to shut the NT down entirely, and make sure I didn't start anything afterwards that I didn't want to leave on. Granted, it only takes about 45 seconds to restart, but it's still annoying and unnecessary. Why doesn't the Nook AppLoader have the 'Back' and 'Options' icons at the bottom of the screen, like other loaders? That could at least allow the option of stopping the app.