Hmmm... every time the script runs, it fetches metar data (small file) from each metar in your list. When your GRLevel3 pulls the placefile generated, it runs the script on your webserver, so yes, it can add traffic to your website's traffic meter. You can reduce the impact be setting the placefile 'fetch/reload' times to every 15 minutes or so.. metars are generally updated only once an hour.