first: this is how Jack has done the layout initialization in his examples
second: that's not the proper way to load JS into the document, maybe you just over simplified it to make it easier to see, but if not here's the right way...
YAHOO.ext.EventManager.onDocumentReady(Layout4.init, Layout4, true);
The problem you're having comes from the fact that the Yahoo! JS library isn't being loaded at all, not that the util.js file isn't being loaded (I'm not loading it at all). Check to make sure that the files are being loaded into the document like above. Also make sure you have your directories right. I kept everything in the directories they came as opposed to throwing everything into 1 directory.
// opening < removed so it would show up
Hopefully this helps