A group of music publishers and songwriters have claimed in a copyright lawsuit that Fullscreen, which operates a network of popular YouTube channels, is including unlicensed music in its videos.

According to a statement from the National Music Publishers Association (NMPA), leaders allege that Fullscreen "directly profits from advertising revenue generated by unlicensed music videos on their channels, but does not compensate songwriters or publishers."

YouTube agreed to pay so that users could freely stick songs into their clips YouTube and the music industry once bickered over the music that users included into their videos. Eventually, YouTube agreed to pay so that creators could freely stick songs into their clips, and that's one of the reasons YouTube is now one of the most popular sources of music online. But these rights apparently don't extend to the growing number of Multi-Channel Networks (MCN) — services that assist YouTube video-makers with such things as promotion, partner management, and digital rights management. According to the NMPA, there are numerous other MCNs not paying for music and this lawsuit could mark the beginning of a protracted legal battle.

Fullscreen is an MCN that services over 10,000 YouTube channels, including those owned by NBCUniversal, Nintendo, and Lexus, according to the NMPA complaint. The publishers also say those channels generate billions of views each — and presumably, lots of money.

David Israelite, NMPA CEO, said in a statement, "Fullscreen's success and growth as a digital business is attributable in large part to the prevalence and popularity of its unlicensed music videos."

A Fullscreen representative was not immediately available for comment.