I think the ruby web server is not necessarily needed, simply change the dotjs.js's content to

$.get(chrome.extension.getURL("script/"+window.location.hostname+".js"), function(script){ eval(script); });

it will look for the js file in the extension directory instead of the local ruby web server, and this should work for any platform. To take the ~/.js convenience, a symlink in *inx system or shortcut in window will do the job.