Q: Can I sell Music from Garageband with Apple Loops?

Yes, you can use the loops in your projects and sell the songs.  The only restriction is, that you must not sell the loops as loops.

If you look up GarageBand at the AppStore, you will see a link to the App Licence Agreement: App License Agreement

You may use the instruments and loops to produce your piece of art, but not distribute them as stand-alone loops or instruments.