From the lengthy blog post under the images, it'd seem he used those archives. I have the impression that I've seen these pictures as TIF files instead of JPGs somewhere (the Internet Archive perhaps?), but I can't remember precisely now. Maybe the author used those, as I imagine they'd give a bit more leeway and flexibility in a restoration effort.
https://www.flickr.com/photos/projectapolloarchive/albums
The link is from a hand full at the bottom of the article, where it also lists other archive overview pages and leads to ~15k scanned photos.