It's apparently genuinely from around 400 AD, regardless of its contents. Thus it's not "Fake but accurate", but rather genuine but innaccurate.
Rather like a thousand years from now finding a recording of the infamous "I did not have sex with that woman" speech by Clinton: It's an actual recording; Bill Clinton really said that; but the contents are of a falsehood being uttered.
No. More like find a copy of the CBS national guard memos 1000 years from now.
Judas never wrote that stuff. As someone else pointed out here, he hung himself before he had time to write a "gospel".