From what I've found CURL is enabled on most servers by default.
The fedex_subscribe.php file is BS.
You need to go to fedex and sign up for an account as a developer (lowest level) The Fedex docs do a great job of stepping you through getting a test meter number, and once your site is ready to go live, how to get a permanent meter number. This is the URL I use but I'm already signed up and cookied in...
drclinks.jsp?links=index.html