I'm a new nuke user, please forgive me if this is one of those dumb newbie questions you've answered 100 times

I just d/l'ed a few themes from here, because I found you all to have some great ones. Of course, I noticed when I implement them at my site that they say 'phpnuke' or 'nukemods.com' at the top. Is it permissible to change this so that it reflects my site name instead? Is there an easy way to do this?

Thanks for your help.

ty97