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="BarbaraMaj3.JPG|1800" />
  </query-continue>
  <query>
    <pages>
      <page pageid="2" ns="0" title="Kabaret Moralnego Niepokoju" />
      <page pageid="519" ns="0" title="Barbara Maj" />
      <page pageid="1092" ns="0" title="Babilon Tour" />
      <page pageid="1800" ns="0" title="Barbara Maj/zdjęcia" />
      <page pageid="1807" ns="0" title="Kabaret Widelec/zdjęcia" />
      <page pageid="1808" ns="0" title="Kabaretowa Noc Czerwcowa/zdjęcia" />
    </pages>
  </query>
</api>