RadControls for Silverlight 2 are not officially available for download, but we sent them to clients who showed interest. Actually, you could get the assemblies even without our permission using Reflector or other tools :-) Silverlight is a client-side environment, which in order to work, should download all assemblies to the client computer, so when you open our online demo, you already have all RadControls for Silverlight 2 assemblies on your PC...
The controls that are running the online demo are far from production quality and will be changed a lot by the official release. That's why we do not provide any support (or at least not at the usual level). If you want to try the controls, I can send them to your email. Just bear in mind that the API will most probably change a lot when we release the official CTP somewhere in may.
Valeri Hristov (Silverlight Team)
the Telerik team