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>
    <alllinks galcontinue="Lehen_super-nodoa_larrabetzun" />
  </query-continue>
  <query>
    <pages>
      <page ns="0" title="Bizkaia" missing="" />
      <page ns="0" title="Buenas Prácticas" missing="" />
      <page ns="0" title="Configura tu ordenador" missing="" />
      <page ns="0" title="Crear un supernodo" missing="" />
      <page ns="0" title="Elige el material" missing="" />
      <page ns="0" title="Empezar una isla desde 0" missing="" />
      <page ns="0" title="Guifi.net" missing="" />
      <page ns="0" title="Konektatu" missing="" />
      <page pageid="21" ns="0" title="Inguruan sor daitezkeen jarduera ekonomikoak" />
      <page pageid="17" ns="0" title="Internet gabe ze interes dauka honek?" />
    </pages>
  </query>
</api>