Interesting!
But isn't the beta connected to your iCloud? So it should not work if you're not invited to the iOS beta?
As I said, I have no idea, since I cannot confirm it myself. I am not invited to the beta, so I downloaded it from here and it worked. Now I don't know if it worked because it is indeed the public beta, or because my device is already registered as a developers' UDID.
I am hearing stories from the forum of dutch site onemorething, where people are installing this one with success, and those people don't have registered devices so you could just give it a shot and see if it works.
If you do decide to use this, be sure to download the version corresponding with the model number on the back of your device and install it through itunes by pressing option+update in the device main screen.