GarageBand Anywhere allows you to put GarageBand on any drive. If you haven't yet installed GarageBand, it can be freshly installed on the drive of your choice. If GarageBand is already installed, it can be moved directly to the desired location.
GarageBand Anywhere will work with any OS X Volume. (From an iPod to a Firewire drive to a RAID array)
GarageBand Anywhere is designed to improve GarageBand's performance and free up space on your boot drive.