Card View gadget appears in the Confluence gadget directory category

During a JIRA Studio blitz test, someone was confused by the GreenHopper Card View gadget appearing in the Gadget Directory Confluence category. He thought the category filtering was broken, but checking the gadget XML, this appears to be intentional:

<Optional feature="gadget-directory"> 
  <Param name="categories"> 
    JIRA
    Confluence
  </Param> 
</Optional>

It's unclear why Confluence was included in the list of categories... it doesn't seem to have anything to do with Confluence.