What do you mean "any other words"? Are there more words in there besides "how"? (Wasn't sure since you didn't show any in your code.
Also, do you know why it's a "badword"? I mean if somebody searches for it, is it going to really slow down the server if it finds it in a lot of posts?
Another question I have, would it be possible to change the message it displays to users? So instead of lying and saying it didn't find it, it says something like, "{boardname} management has disallowed a search of that word."
I don't know what the name thing is to pull the name of the forum, but you get the idea.