LOL... Define release forms... If you're going to use someone else's screenplay, then really, you need a contract between yourself and the screenwriter.
A release form is something you would have your actors sign... Or owners of locations you want to use... I don't know too many screenwriters that would sign some kind of release form concerning their screenplay. I know I wouldn't...
Even if you're not paying for the script... You need a contract between yourself and the screenwriter.