SCION works for Windows Store apps if you override these platform values in this way.

scion.windows-platform.js

ajax : WinJS.xhr,

getDocumentFromUrl : function(url,cb){
    this.ajax({ url: url }).then(
        function (r) {
            cb(null,r.responseXML);
        },
        function (e) {
            cb(e);
        }
    );
}