I checked the book out from the library. Is there a way that I can still get access to the code archive??
I’m not sure, you would be better off sending an email to Sitepoint’s support people. I am surprised though that SitePoint don’t offer their code archives on the book’s main pages (rather than requiring a login) - the content of the book is what is of value, the examples just build upon them. 
As Alex said, you’d be better of contacting the Post-sale department and asking them (http://www.sitepoint.com/books/contact.php). I never had a problem retrieving the code archive, even after a long time but I don’t know if that still is true.