Using nulled software is a violation of copyright law. If a developer or Envato (the parent company of CodeCanyon) discovers you are using their IP without a license, they can:
For the uninitiated, a "nulled" script is a pirated version of premium software. Hackers remove licensing checks (hence "nulling" the verification calls) and repackage the script for free download on shady forums or file hosts. codecanyon nulled php
While it may be tempting to get premium software for free, here is why you should avoid nulled scripts: Using nulled software is a violation of copyright law