We have not written a databinder for the DevExpress RadioGroup. Without this, I don't think there is a way to make this work.
Here, as I see it, are your choices:
(1) Use .NET GroupBox and RadioButtons as is shown in the Tutorial instead of the DevExpress RadioGroup.
(2) Request a Feature Enhancement and hope that we will implement the feature some day.
(3) Build a Custom DataBinder for the DevExpress RadioGroup. You would probably need the source for the .NET RadioButton DataBinder, but if you had the source, it should be fairly straightforward to build the DataBinder. Essentially, you would replace DotNetRadioButton.Tag with DevxRadioGroup.Item.Value.