This happens because Respond.js does not work when a page is loaded directly from the hard drive and not from a web server. And without Respond.js IE8 can’t load the desktop styles and that’s why it displays the mobile-first collapsible version of the menu.
If you install the demo on a web server and load it via http/https it should work just fine in IE8.
Sorry for this delay! Just got back from my summer vacation.
v0.9.7 isn’t mobile first and doesn’t need Respond.js to render the desktop styles in IE7/8. Not sure why it didn’t work when you accessed the demo via a web server. If you install the default demo on a web server and load it via http://…, it should work just fine – it’s practically the same as loading: