Notorious Norwegian hacker Jon Lech Johansen, also known as "DVD Jon," is preparing for another run-in with the music industry after he released software that lets iPod owners play music bought from iTunes on non-Apple devices.

The free PC-only program, called DoubleTwist and available for download, allows people to drag and drop songs from iTunes into folders on their desktops.

It then in turn copies the files to devices such as mobile phones and games consoles, as well as letting users share songs online.

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In doing so, the software breaks Apple's FairPlay copy-protection encryption — also generically known as digital rights management or DRM — which is built into all Advanced Audio Coding-format music files bought through iTunes.

FairPlay-encrypted files can normally be played only on Apple products such as iPods, iPhones, Apple TV set-top boxes and Macs and PCs running iTunes.

Apple also sells DRM-free MP3 files through iTunes. Those files cost a bit more, but can already be played on any digital music player and copied endlessly.

Johansen's company, also called DoubleTwist, maintains that its service is legal, but lawyers said that Apple would almost certainly seek to shut it down because the law now specifically targeted technologies which attempted to circumvent DRM.

Johansen has previously enabled iPod owners to play music bought from Web sites other than iTunes.

DoubleTwist's new software will initially enable files to be copied to Nokia N-series mobile phones, Sony Ericsson's Walkman and Cybershot handsets and as any smartphone powered by Microsoft's Windows Mobile operating system.

The program gets around Apple's DRM software by replaying a song in fast-forward and making a copy of the audio track using a process similar to that by which each track on a CD — actually a data file itself — is "ripped" or converted into an MP3 or AAC file.

About 100 can be converted in half an hour using DoubleTwist's software, the company said, although there is a 5 per cent loss of sound quality.

The San Francisco-based company said that its software was legal, because it only allowed a user who has already purchased music to copy it.

"All we are facilitating are friends sending things to one another," Monique Farantzos, DoubleTwist's chief executive and co-founder, told Reuters.

Lawyers cast doubt on Ms Farantzos's claims, however, saying that the law had taken steps to protect Apple's efforts to control the way its music could be played, and that anyone circumventing measures such as DRM risked being found guilty of copyright infringement.

"I would be astonished if DoubleTwist doesn't get a call from Apple," said Paul Jones, a partner in intellectual-property law at the London-based firm Harbottle & Lewis.

Johansen has been an arch-enemy of the music and film industries ever since the day in 1999 when he and two other hackers, who remain anonymous, released DeCSS, a widely distributed bit of software which cracked the CSS copy-protection key on Hollywood-studio DVDs.

Johansen claimed he and his co-crackers were simply trying to play DVDs on their Linux-based computers — the free operating system's DVD software did not license CSS from its maker — but they also released a version that would work on Windows as well.

Johansen, now 24, was 16 at the time. He was later tried twice in Norwegian courts of computer hacking in the DeCSS case and acquitted both times.

In 2003, Johansen developed the first of several programs which attempted to bypass the system developed by Apple for synchronizing its iTunes store with iPods, leading to one of a series of run-ins with the firm.