Download from http://visualstudiogallery.msdn.microsoft.com/36925113-cdce-4953-a5d6-fb3d2912dad7 

The download page at http://o.oz-code.com/download states "The beta version is Free until the first release version, after which the product will be available for purchase. The prices for the 1.0 release have already been set and can be viewed on our purchasing page."

Have a read of the overview at http://o.oz-code.com/overview - this promises to be a very useful debugging tool.