These are resources which are needed in order to integrate WebViewers into your web application framework. How exactly WebViewers are implemented is largely an implementation detail and you can find more information here http://webviewers.org/xwiki/bin/view/Main/WebApplicationTutorial but these files are necessary in order to instanciate a WebViewer.
This example makes use of the textedit-webviewer which is available in the
webviewers github repostitory.
<html>
<head>
<script src="renderjs_jquery.js"></script>
<script src="jschannel.js"></script>
<script src="renderjs.js"></script>
<script>
rJS(window).ready(function() {
var root = rJS(this);
var elem = document.getElementById('webviewer');
root.declareIframedGadget("path/to/webviewer/index.html", elem).done(function (gadget) {
gadget.setContent("hello world!");
});
});
</script>
</head>
<body>
<div id="webviewer"></div>
</body>
</html>
The WebViewer should have the file renderjs-stub.js which is provided.