Edit in JSFiddle

function go() {
  var apiKey = document.getElementById("apiKey").value;
  var resultDiv = document.getElementById("result");
  var rawResultDiv = document.getElementById("rawResult");
  try {
    Gp.Services.getConfig({
      apiKey: apiKey,
      onSuccess: function(result) {
        rawResultDiv.innerHTML = "<p>" + JSON.stringify(result) + "</p>";
        // interpretation des resultats
        var strResult = "";
        var lconf = result.getLayersConf(apiKey);
        // droits
        strResult += "<b>Ressources disponibles (" + Object.keys(lconf).length + ")</b> : <br/>";
        for (var lk in lconf) {
          var lstr = "";
          lstr += lconf[lk].title + ' (' + lconf[lk].name + ') - service : ' + lconf[lk].serviceParams.id;
          strResult += "* " + lstr + "<br/>";
        }
        // WMTS layer conf
        strResult += "<br/><b>Paramètres de la couche WMTS ORTHOIMAGERY.ORTHOPHOTOS</b> :</br>";
        var lortho = lconf["ORTHOIMAGERY.ORTHOPHOTOS$GEOPORTAIL:OGC:WMTS"];
        if (lortho) {
          strResult += "* server URL : " + lortho.serviceParams.serverUrl[apiKey] + "<br/>";
          strResult += "* layerName : " + lortho.name + "</br>";
          strResult += "* projection : " + lortho.defaultProjection + "</br>";
          strResult += "* format : " + lortho.formats[0].name + "</br>";
          strResult += "* style : " + lortho.styles[0].name + "</br>";
          strResult += "* tms : " + lortho.wmtsOptions.tileMatrixSetLink + "</br>...";
        }
        // TMS..
        strResult += "<br/><b>TileMatrixSets disponibles</b> :</br>";
        var tmss = result.getTileMatrixSets();
        for (tms in tmss) {
          strResult += "* " + tms + " (" + tmss[tms].projection + ")<br/>";
        }

        resultDiv.innerHTML = "<p>" + strResult + "</p>";

      },
      onFailure: function(error) {
        rawResultDiv.innerHTML = "<p>" + error + "</p>";
      }
    });
  } catch (e) {
    rawResultDiv.innerHTML = "<p>" + e + "</p>";
  }
}
// affichage version bibliothèque
var infoDiv= document.getElementById("info") ;
infoDiv.innerHTML= "<p>Biblitohèque d'acces "+Gp.servicesVersion+" ("+Gp.servicesDate+")</p>" ;

<div id="params">
  <p>Clef Géoportail :
    <input type="text" id="apiKey" value="cartes" />
  </p>
</div>
<div id="go">
  <input type="button" value="GetConfig" onclick="go()" />
</div>
<div id="result"></div>
<div id="rawResult"></div>
<div id="info"></div>

#params {
  width: 100%;
  height: 50px;
  box-shadow: 0 0 10px #999;
  font-family: monospace;
  padding: 5px;
}

#go {
  padding: 5px;
  float: center;
  width: 100%;
  height: 30px;
}

#result {
  padding: 5px;
  width: 100%;
  height: 350px;
  box-shadow: 0 0 10px #999;
  font-family: monospace;
  overflow: scroll;
}

#rawResult {
  padding: 5px;
  width: 100%;
  height: 300px;
  box-shadow: 0 0 10px #999;
  font-family: monospace;
  overflow: scroll;
}
#info {
    height : 20px;
    width: 100%;
    font-family: monospace;
    font-size: 10px;
}