You are looking at the HTML representation of the XML format.
HTML is good for debugging, but is unsuitable for application use.
Specify the format parameter to change the output format.
To see the non HTML representation of the XML format, set format=xml.
See the complete documentation, or API help for more information. 
<?xml version="1.0"?>
<api>
  <query-continue>
    <allfileusages gafcontinue="Bomulus1.jpg|57" />
  </query-continue>
  <query>
    <pages>
      <page pageid="51" ns="0" title="Bike Baron" />
      <page pageid="682" ns="0" title="Bloody Afternoon" />
      <page pageid="822" ns="0" title="Project Black Sun" />
      <page pageid="3564" ns="0" title="Bad Piggies" />
      <page pageid="3568" ns="0" title="Bjong" />
      <page pageid="3895" ns="0" title="Bad Air Day" />
      <page pageid="3928" ns="0" title="The Blobjob" />
      <page pageid="4027" ns="0" title="Badland" />
    </pages>
  </query>
</api>