and do they trust anyone report a nulled script? even for that someone for most cases it can not be easy to find out whether a script nulled or original, right ?
What does a script has to do with google and adsense?? If they would care about such things, you wouldn't find a single warez site on the search! Starting TPB.
It really depends on the script. vBulletin, for example, has both a form you can use if you know someone is illegally using their script, and has hired a company to look for/investigate reports and if they find a nulled script in use they try to get the site taken down. Other companies aren't quite as proactive. However, if someone reports you to the company that makes the script they can file a take down notice both with your host and with Google.