Which Gnutella program are you using? You've posted into a general gnutella network discussion section, not a gnutella client program section. The answer depends upon which client you use. As for an overview of gnutella freedoms, see Quality of Content on the Network (click on link)

Edit: Checking your previous thread, you're using LW. So my advice would be to bite a piece & do this Direct instructions to eliminate porn from results & also How to use the Keyword Filter