ezkeyword datatype isn't implemented in ezodf extension (ezooimport.php).

Suggested code:
—
case "ezkeyword":
{
$keyword = new eZKeyword();
$dom =& $xml->domTree( $xmlTextArray[$sectionName] );
$text = eZOOImport::domToText( $dom->root() );
$keyword->initializeKeyword( $text );
$dataMap[$attributeIdentifier]->setContent( $keyword );
$dataMap[$attributeIdentifier]->store();
}
break;