In a case that could have widespread impact on how to divvy up digital download revenue, Eminem's music publisher has filed has filed a multimillion-dollar lawsuit against Apple over iTunes downloads, alleging the company is violating copyrights by selling the rapper's songs online.

Eminem in the iTunes ad.

Apple has the permission of Eminem's label, Universal Music Group and its subsidiary Interscope, to sell Eminem's music, but the lawsuit claims that Eminem's music publishers, Eight Mile Style and Martin Affiliated, have not authorized the downloads, and iTunes is this committing copyright infringement.

"Eight Mile and Martin have demanded that Apple cease and desist its reproduction and distribution and Apple has refused," the complaint states.

The complaint, filed yesterday in US District Court in Detroit, shines light on a long-simmering debate in the music business over who controls online distribution of music and who gets how much of the revenue from downloads. While publishers hold music copyrights, record labels have traditionally received the lion's share of revenue from sales.

Publishers have increasingly argued that digital downloads should be classified as a licensing agreement rather than a sale, thus putting more control--and revenue--in the hands of the publishers. Under a licensing arrangement, the record label and music publisher would receive an equal cut of the revenue. If it's classified as a sale, the publisher receives only a royalty fee, a much smaller sum.

This is the second time Eight Mile has sued Apple. The first complaint, filed in 2004 over the use of Eminem's image and his song "Lose Yourself" in one of iTunes' famous silhouette ads, resulted in an out-of-court settlement.

The legal news comes on the heels of Apple's announcement today that iTunes has sold more than 3 billion songs, overtaking Amazon.com as the third-largest music retailer in the US. The milestone comes just six months after iTunes surpassed the 2 billion mark.