Allow jsxgraph board in a new window (opend by window.open())
The board attribute is: initBoard('box', {document: documentObj});
Example:

clickme = function() {
    var plotWindow = window.open("", "JSXGraph-Window", "width=500,height=500");
    var htmltxt = '';

    htmltxt += '<html>';
    htmltxt += '<head>';
    htmltxt += '<title>JSXGraph </title>';
    htmltxt += '<link rel="stylesheet" type="text/css" href="../../../jsxgraph/distrib/jsxgraph.css" />';
    htmltxt += '</head>';
    htmltxt += '<body>';
    htmltxt += '<div id="jxgbox2" class="jxgbox" style="width:400px; height:400px;"></div>';
    htmltxt += '<body>';
    htmltxt += '</html>';

    plotWindow.document.open();
    plotWindow.document.write(htmltxt);
    plotWindow.document.close();

var b2 = JXG.JSXGraph.initBoard('jxgbox2',
    {boundingbox: [-5, 5, 5, -5], axis: true, showcopyright: false, shownavigation: true, document: plotWindow.document});
var p2 = b2.create('point', [-4, 1], {});
var p3 = b2.create('point', [4, -1], {});
var l = b2.create('line', [p2, p3], {});

};