RadListBox does not support such Group (Header) Items out-of-the-box.
Alternatively you can use Templates (for those Header Items) to visually differentiate them from other Items. Then you can handle the client-side SelectedIndexChanging event and cancel it if a Header Item has been clicked (Header Items could have unique values, e.g. -1).
As for transferring back an Item to the source ListBox you can handle the client-side Transferred
event and then reorder the Transferred Item(s) to their respective Group.
The SelectedIndexChanging event is not yet documented, still it is identical to SelectedIndexChanged with the only difference that it can be canceled (eventArgs.set_cancel(true)).
I hope this gets you started.
the Telerik team