I saw this on the bnet forums, and file planet does have a signup page for upen beta, and you do get a cd key. the only bad thing is that thousands of people are now trying to get to www.worldofwarcraft.com so good luck trying to get anywhere.
http://www.fileplanet.com/betacenter/wow_open/signup/?f=147141
http://www.fileplanet.com/betacenter/wow_open/signup/?f=147141