Sorry, it is fake. Just take a look at some the arguments presented by an experienced leak handler: https://twitter.com/stagueve/with_replies
There is some minutiae that is easily cleared up when you take into account that the iOS 8 build is one nobody has seen before. Maybe the hardware wasn't assembled to the tee, maybe it didn't make it through quality control, but that software could not be forged by anyone other than Apple, and when has Apple software ever been ported flawlessly to a non-Apple phone?