Requiem is a freeware which is able to help the iTunes media get rid of FairPlay DRM encryption ( a DRM technology developed by Apple Inc). It can remove DRM without any quality loss and with no decoding or re-encoding. Requiem is available on Windows, Mac, and Linux. It used to be popular among Apple users, but it stopped to upgrade from V4.1 in 2012.
Although Requiem has been successful for owning a large consumer groups, it was defeated in the fierce competition with Apple Company. Apple manages to restrict this program in 2012. So Requiem failed to be compatible with higher version than iTunes 10.7. In other words, if you want to use it, you have to downgrade your iTunes to V10.7 or lower.