There is no doubt that Requiem was the wonderful free iTunes DRM removal tool in 2013.
But now, the end of 2017, the most popular
iTunes m4v drm removal tool could be DRamre M4V Converter, which you can purchase this at up to 50% discount from its
Christmas sales promotion since Requiem claimed officially Requiem is the last release in the market. It may not work in some computers with the new iTunes version 10.8 or above directly. I would not advise to downgrade the operating systems and iTunes versions.
By the way, no matter which DRM removal tool you choose, you must install iTunes store on your computer currently.
Have a great Christmas time.