LR 2.0 Beta is available for anyone to download from the adobe.com site. If you have a license for LR 1.x, then you can use the LR 2 beta until the end of August. Otherwise you can use it for 30 days, unless 'invited' by someone with a LR 1.x license.
After readiing Ian Lyons review, "Unlike the "Public Beta" for Lightroom 1.0 Lr2beta is pretty much "feature complete"," I had the impression that they are two different releases. Maybe, I am in error.