My interpretation was/is that they're both right. The word originated as 'wares with a Z' but once it was spelled that way it became natural to pronounce it 'ware-ez' but nobody thought you were unintentionally mispronouncing it. The in-joke continued on certain boards as 'warez' became 'Juárez'...
It absolutely is pronounced "wares" as in "software" but 13 year old me didn't know that so I and everyone I knew pronounced it "war-ezz", as in "warfare".