Originally posted by: Zion
From IMDB:

Directed by
Kevin Munroe

Writing credits
Kevin Eastman (creator Teenage Mutant Ninja Turtles comic book & characters) &
Peter Laird (creator Teenage Mutant Ninja Turtles comic book & characters)

Kevin Munroe (written by)

http://imdb.com/title/tt0453556/fullcredits#writers

I'm guessing that's just saying that they were the creators of the characters and original stories.

The official movie website does not mention them as writers of this new story. Neither does the official website for the teenage mutant ninja turtles (which is where I'd expect to find any information relating Peter Laird or Kevin Eastman to the story):

http://www.ninjaturtles.com/html/movies.htm