The beta build of Mac OS X 10.5 ‘Leopard’ that Apple handed out to developers on June 11 at its Worldwide Developers Conference (WWDC) has leaked to the internet and is being downloaded by users of PirateBay, the Swedish torrent tracker.

Apple CEO Steve Jobs spent most of this 90-minute WWDC keynote address touting the upcoming OS, which is set for release in October. Eight days later, the beta labelled build ‘9A466’ was uploaded to PirateBay.

The first upload didn't take - there was only one ‘seeder’, the term for a computer that has a complete copy of the torrent file - but the second yesterday is being downloaded and assembled, according to comments left by numerous users.

As of late yesterday, only four seeders were available, with 181 ‘leechers’, or computers that have downloaded only part of the complete torrent. By yesterday, however, the numbers had climbed to 44 seeders and more than 1,500 leechers.

The beta was also posted to the private, invitation-only torrent tracker Oink yesterday, according to CrunchGear, a tech blog. But when CrunchGear exposed the leak, Oink pulled the beta. That sent the downloaders into a verbal rage during which they vented their collective spleens at the blogger who outed Oink. "go [expletive deleted] yourself you [expletive deleted] rat," ranted one.

Based on the PirateBay listing, the Leopard 9A466 beta weighs in at just over 6GB. But the exact byte count worried a user tagged as ‘konelli’.

"It's definitely not my intention to spoil the party, but how do we know that this is the real thing? Last time I checked the WWDC version was supposed to be 6.94GB (or 7,450,640,384 bytes). This is, well, less. Has anybody finished downloading who could confirm that this is genuine?"

Apple was asked if it planned to pursue the person or persons who leaked the build to BitTorrent, or what actions it might take against PirateBay. It did not immediately respond with comment, however. The first question is especially important in light of past history. The last time an under-development version of Mac OS X ended up on BitTorrent, Apple brought out its lawyers.

In December 2004, Apple sued three men, as well as 25 others identified only as ‘Does’, for releasing a developer preview of Tiger, Mac OS X 10.4, via the BitTorrent file-sharing network. All three were members of the company's own Developer Connection, Apple claimed, and had illegally leaked their copies of Tiger. But after several Apple notables, including co-founder Steve Wozniak, pleaded for leniency in blogs and other online postings, Apple backed off a bit.

During a ten-month span from March to December 2005, Apple signed settlements with the three named defendants: students Vivek Sambhara, David Schwartzstein, and David Steigerwald. Each promised to never again release information about the company or its products, while media accounts reported that Schwartzstein and Steigerwald also distributed repentant statements and paid damages to Apple.

"We are pleased that Mr Steigerwald has taken responsibility for his actions and that we can put this lawsuit behind us," Apple spokesman Steve Dowling told the Associated Press in March 2005 after the company settled with David Steigerwald, then a 22-year-old North Carolina college student.

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