Mac OS X 10.6 Snow Leopard, build 10A222. This is the most current build available to Apple Developer Connection members as of January 2009.
Someone has uploaded this build, along with Mac OS X Server 10.6, build 10A222 and the Kernel Debug Kit for the build, to Demonoid, with the requirement that the torrent will be immediately removed if it shows up on any other torrent site. In addition to this restriction, the uploader set the private bit on the torrent, disabling DHT and preventing a btReannounce once the torrent is removed.
OS X-Files, a Mac OS X-related torrent aggregator picked up the torrents, which the uploader viewed as a violation of the Demonoid-exclusivity rule, and immediately pulled the torrent from Demonoid, which, together with the private bit, resulted in the complete death of the torrent.

This torrent is an edited version of the Demonoid torrent with the private bit removed and the Pirate Bay tracker URLs added to prevent another takedown.

Note: This torrent is ready to download now.