Well, my English language teacher taught us that the acronym comes from the San Francisco equality marches during the 60s, where gay men and women held up plaques and signs of 'We're As Good As You' or something. So if my teacher is anything to go by, yes, gay does come from 'good as you'
Wow, I never knew of this acronym, but it's awesome! I always thought that "gay" in its modern iteration had just been adapted from the older usage, meaning "happy" lol