You'd have to figure the use of the word to mean homosexual came from #3, as in licentious.
Goes back further than most people think. There are references to gay as homosexual by Noel Coward in the 1920s when he wrote this referring to Oscar Wilde.....
Pretty boys, witty boys,
You may sneer
At our disintegration.
Haughty boys, naughty boys,
Dear, dear, dear!
Swooning with affectation...
And as we are the reason
For the "Nineties" being gay,
We all wear a green carnation.
Foppish, Dandyish and gay to boot.
This is now the second gay thread on SailNet. Better be careful chaps, you're starting to show a bit too much interest in the subject.
The other thread is pretty upset, it thought it was the only gay in the village.