Usage rights for iTunes Store purchases on Mac
Movies, TV shows, and certain other items purchased from the iTunes Store are protected by Digital Rights Management (DRM). These protected purchases can be:
Played on up to five authorized computers
All songs offered by the iTunes Store now come without DRM protection. These DRM-free songs, called iTunes Plus, have no usage restrictions and feature high-quality 256 kbps AAC (Advanced Audio Coding) encoding.