A simpler method is just to see if the curl_init function is present. If it is, Curl is installed.
Create a new PHP file, call it 'curl.php'. Inside this file type the following only:
<?php
echo (function_exists('curl_init') ? 'OK' : 'FAIL');
?>
Upload to any public location on the server where you'll be transmitting license data and access in your browser. If you see 'OK', curl is installed. If you see 'FAIL', it isn't and you need to recompile your server WITH curl support or contact your hosting company.