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>
    <allpages apcontinue="Running_Gideros_Studio_under_Linux" />
  </query-continue>
  <query>
    <allpages>
      <p pageid="17" ns="0" title="Build Gideros On Mac" />
      <p pageid="15" ns="0" title="Build Gideros On Windows" />
      <p pageid="11" ns="0" title="Code of Conduct" />
      <p pageid="6" ns="0" title="Deployment" />
      <p pageid="13" ns="0" title="Forum FAQ" />
      <p pageid="7" ns="0" title="Gideros plugins" />
      <p pageid="4" ns="0" title="Installing Gideros Studio" />
      <p pageid="1" ns="0" title="Main Page" />
      <p pageid="10" ns="0" title="Menu shortcuts and accelerators" />
      <p pageid="2" ns="0" title="Release notes" />
    </allpages>
  </query>
</api>