You shouldn't buy an application or any good from someone unless they're recognized as sellers by the official developers. If you know the software is working only with a dongle, then this is the way the app is activated and buying something without the device, might get you an application that will never work.
I've checked the official website and Onyx-RAD doesn't appear to be available anymore. There is another product called Opal-RAD. You might want to check that one instead through the following link: http://viztek.net/products/opal-rad/