Video Star...

This is an amazing app! So fun to do with friends and family. I love this app but I have one question, what does it mean by non-DRM song. Ever time I get a new song after the IOS update it wont let me do the song on video star. The main reason I download song is just for video star. Please help or fix.

kgpsoccer05 about Video Star, v5.3.1