It may be authentic since there's an option to download it for the 8830 in Blackberry Desktop Manager v4.7 via Application Loader -> Update Software, so at least the OS version is correct, even if it isn't for 8330.
Not a stupid question at all since I was confused at first. Each release is for a different device. For example, an 8110 OS will not work on an 8120 device, and so on. The carrier that it's released on is irrelevant since the instructions are posted in many places on how to upgrade your device using ANY wireless carriers OS. You just have to get the right OS for your device.
I know. Waiting for the 8330 releases is painful but they are taking a back seat to the Bold and Storm releases, AFAIK.