In theory the beta version of Office 12 (released a couple of weeks ago) is only available to a select group of MS testers. In reality it leaked out and is available to almost anyone who has a little time to look for it and the patience to download it. If you're interested try Googling for Office 12 Beta or you can download it here provided that you have the appropriate download software. There was an earlier version that was built in June 2005 that was also leaked. That is NOT the beta version.
This is kind of boring, but here is a copy of the original email that MS sent to prospective testers of Office 12.
MS has not commented on any planned legal action against sites that host the leaked download. I can't imagine why they would care, it seems like the more feedback they get the better the end product will be.
We Report. You Decipher.