If it says "Something by _____" then how is it you who created the script? Did you actually write the code that made the script? Are you getting confused between creating the script and downloading it?
If you downloaded a script from a website, then whilst it's possible to remove the credits, we couldn't really tell you how to do it, because we don't know about all the different scripts. Secondly, it's not very good to remove the credits for someone elses work.
If you did create the script, then surely you would know how to remove it?
Regards,