I don't think the sky is really that bright. If you read the caption the object that is so bright near the center is the Andromeda galaxy. Since Andromeda is blown out, apparently it was taken with a very high ISO and the landscape was either illuminated by the moon in back of the photographer, or just by starlight.
Ahaa! Yes, I missed the reference to the Andromeda galaxy. I thought it was the moon and couldn't figure out how he did it since one usually has to wait for a New Moon to see the MW properly.