In the 15 months since the US Supreme Court's landmark decision on peer-to-peer file sharing, most of the major P2P outfits have either paid settlements to the RIAA and folded or gone legit.

LimeWire CEO Mark Gorton

All but two, that is.

While Morpheus operator Streamcast, one of the named defendants in that landmark case, continues its legal battle with the music industry, another P2P giant is fighting back.

LimeWire, sued by the major record labels last month for copyright infringement, filed a countersuit yesterday in US District Court in New York, alleging antitrust violations, consumer fraud, and anticompetitive practices.

In the complaint, LimeWire doesn't address the copyright infringement claims against it. Instead, the suit argues that the major record labels "have unreasonably and concertedly refused to do business with LimeWire," in an attempt to "prevent the use of decentralized peer-to-peer technology for the secure distribution of licensed, copyrighted content."

The complaint based its anticompetitive practices charges on digital music ventures that the major labels have or have had stakes in, such as digital retail platform maker MusicNet and failed online retailer pressplay, which eventually became the latest version of Napster.

The countersuit also points to the labels' relationship with Mashboxx and iMesh, two of the industry-supported legal P2P services. The claim says that P2P firms seeking to go legit have been forced to adopt the model used by iMesh, which uses acoustic fingerprinting technology developed by Audible Magic to police its networks of illegal files.

"The [labels] have concertedly promoted the distribution of licensed content through companies in which many of the [labels] and business affiliates have or had direct equity interests, such as MusicNet, pressplay, and Roxio, or through business entities that they have a relationship with, such as iMesh or Mashboxx," the counterclaim reads.

But in an email, Mashboxx CEO Wayne Rosso told MP3.com that although securing licensing deals from all four major labels has been "an extremely thorough" process, his firm hasn't been forced to adopt one particular solution.

"As far as I know, neither the RIAA or any of the labels have insisted or even suggested that Limewire or any other P2P use a specific solution if they desired to become an authorized service," Rosso wrote.

"This case is but one part of a much larger modern conspiracy to destroy all innovation that content owners cannot control and that disrupts their historic business models," the counterclaim alleges.