"Authorized for use by" is the method that the digital sheet music industry uses to prove the purchase of a digital sheet music product. This is needed by many musicians, etc. for performances, auditions, and competitions as proof that they did in fact purchase the music and did not just make a photo copy of someone else's sheet music.
The "Authorized for use by" name that prints on your digital sheet music cover page is proof that you purchased the music and are authorized to use it. It is set when you set up your account, and may be changed by editing your Billing information through your account settings.