The author will not take legal action against George Lippert, who wrote a follow-up to Harry's adventures on his website.
Under copyright laws Lippert could have been prosecuted for his actions.
Rowling's lawyers confirmed she is happy for spin-offs to be published online as long as the publications are not sold and it is made clear she was not involved in the stories.
She also requested the follow-ups do not contain pornography or racism.
Meanwhile, Rowling - who has seen the 'Harry Potter' books turned into blockbuster movies - has been voted entertainer of the year by Entertainment Weekly magazine.
The publication insisted she deserved the title for getting "people to tote around her big, old-fashioned printed-on-paper books as if they were the hottest new entertainment devices on the planet".
The magazine also named George Clooney a "valedictorian" because he has "deftly balanced box-office viability with personal responsibility".
TAGS: Entertainment Harry PotterRowling