It may be because of the angle it was signed but the Phil Rudd looks a little strange to me. I would be pretty confident in it being good though. The other signatures are definitely spot on. Rudd maybe too, just a strange angle.
The guitar was supposedly a gift given to record executive Michael Klenfner by ACDC. Klenfner passed away in 2009 and his widow auctioned off a lot of his stuff earlier this year. I guess he had quite a collection. I wish one of the band members would have dated it. ACDC doesn't seem to date their autographs like many musicians do.