Bought both Toy Story 3 & Toy Story 4 from Script City-- they ARE legit.
From The Lost Media Wiki
Just bought both of the scripts today and received the PDFs in the e-mail. : ) Scanning them over, they are both definitely early drafts and bear very little resemblance to the final product. It says, "Writer's First Draft 5.17.13" on the main page, and yes-- it's attributed to Ben Karlin. My guess is this was the VERY FIRST version of Toy Story 4, since Toy Story 4 wasn't announced until 2014. So-- no, this isn't Rashida Jones' version, but YES, it's legitimate!