It looks like the version of miletracker I have is looking for a URL to check and see if it is expired. I found this in the log file that is in the Miletracker folder. Going to that URL shows the result "expire-no|". I bet it's checking the user agent when you hit the URL and comparing it with the latest version.

Couldn't one just modify their host file to point to another server and create a simple php script to output "expire-no|" to get the program to not expire?

I'm going to test it when I get home.