You are looking at the HTML representation of the mFormat?> format.
HTML is good for debugging, but probably is not suitable for your application.
Please see "format" parameter documentation at the API help for more information. 
<?xml version="1.0" encoding="utf-8"?>
<api>
  <query>
    <general mainpage="Main Page" base="http://www.barcampbank.org/index.php/Main_Page" sitename="BarCampBank's Wiki" generator="MediaWiki 1.10.1" case="first-letter" rights="" />
    <namespaces>
      <ns id="-2">Media</ns>
      <ns id="-1">Special</ns>
      <ns id="0" />
      <ns id="1">Talk</ns>
      <ns id="2">User</ns>
      <ns id="3">User talk</ns>
      <ns id="4">BarCampBank's Wiki</ns>
      <ns id="5">BarCampBank's Wiki talk</ns>
      <ns id="6">Image</ns>
      <ns id="7">Image talk</ns>
      <ns id="8">MediaWiki</ns>
      <ns id="9">MediaWiki talk</ns>
      <ns id="10">Template</ns>
      <ns id="11">Template talk</ns>
      <ns id="12">Help</ns>
      <ns id="13">Help talk</ns>
      <ns id="14">Category</ns>
      <ns id="15">Category talk</ns>
    </namespaces>
  </query>
</api>