Because ZeroClipboard is flashed based, it's bound to the limitations that Adobe has set forth:
Note: Content running in Flash Player or in a non-application sandbox in AIR can call the getData() method only in an event handler for a paste event. In other words, only code running in the AIR application sandbox can call the getData() method outside of a paste event handler.
Therefore, no, you cannot get the contents of the clipboard outside of a paste
event.