Apologies, this kind of stuff should be directly supported. For now you can use the snippet below.
Note, rename/copying a world is actually very straightforward, the only issue that you have to pay attention to is to properly link the bootstrap script since this is link is relative and needs to change when you change the location of the world.
function copyWorld(from, to) {
// usage like:
// copyWorld('users/robertkrahn/foo/world.html', 'users/robertkrahn/world.html');
var toURL = URL.root.withFilename(to),
htmlSource = URL.source.asWebResource().get().content,
html = $($.parseHTML(htmlSource, document, true/*keep scripts*/)),
bootstrapModuleURL = new URL(module("lively.bootstrap").uri()),
bootstrapFile = bootstrapModuleURL.relativePathFrom(toURL);
html.filter('script[src]').attr('src', bootstrapFile);
var newHTML = html.toArray().map(function(ea) { return Exporter.stringify(ea); }).join('\n');
toURL.asWebResource().put(newHTML);
}