About License

Hello, i wanted to ask about PHPStorm license, i had one and it was  expired 26.02.14, but i still can use it, i get only on start message  "Upgrade Subscription Your PhpStorm upgrade subscription has expired.  Renew your subscription before 26.02.14 to get new PhpStorm versions as  soon as they are released." But all still works, i can update/upgrate my  IDE, few minuts ago i updated to 7.1.3 version, and all ok. So i want  to ask what restrictions ill get with that not-upgraded version ? And  why i still can use it. Anyway i'll upgrade my PHPStorm, but just interesting why i still can use it and update. Thanks :)