The brand new Napster 2.0 Beta 6 supports Microsoft’s Windows Media Audio format. The addition may give the file-swapping software provider some much-needed legal cover against the 18 separate suits alleging, among other things, that the company encourages copyright infringement by its hundreds of thousands of users.

What this means is, in addition to MP3 files, Napster users can swap copyright-protected WMA files, which require users to download a “key” to play.

The support of a copyright-protected format may lend at least some credence to Napster’s claims that it is a “mere conduit” for the trading of software files under the digital Millennium Copyright Act.

Judge Marilyn Hall Patel recently denied Napster’s request for summary judgement in its case with the RIAA, which utilized that defense.

As the various suits against Napster move forward in the courts, a key defense will be to show the Napster software has “substantial non-infringing uses” in addition to its very popular and now-notorious MP3 file directory.

In other Napster news, more than 30,000 users banished from the site at Metallica’s insistence have notified Napster that they want back in.

The disenfranchised users allege they were misidentified as persons illegally bartering Metallica’s copyrighted tunes in MP3 format.

“The fact that so many people have come forward and disputed Metallica’s accusation that they did not break the law demonstrates that this is not a black and white issue,” Napster’s 19-year-old founder Shawn Fanning said.

Napster had posted information on its Web site telling users how to file a counter notification if they felt they had been wrongly identified. The company has been forwarding the petitions to Metallica’s attorney, who disputed the claims.

“They’re absolutely lying. There’s no question that they’re lying,” said attorney Howard King. “Each and every one of them was offering Metallica MP3s for uploads.”

In addition, rapper Dr. Dre – by way of the attorney he shares with Metallica – lifted part of a Metallica performance of sorts on May 17.

Rather than outright copy Metallica drummer Lars Ulrich’s recent personal appearance at Napster headquarters, Dre and King instead emailed and faxed the names of 239,612 alleged MP3 traders to Napster. In a statement, Dre informed Napster he would prefer the 935,500 recordings available for download be removed rather than users from the service. But if the Metallica case has set a precedent, most of those traders can expect to be at least temporarily blocked from using Napster.