When you check it out, it appears that 'gay' has shared usage in its history. And there is nothing other than one's own qualms stopping anyone from using it in any way one wishes even today. For instance, I would not hesitate to use the word in a song, used appropriately such as a bird's trill or a happy party. (Frankly, given the article below, I'm not so sure that gay people would approve of all of its usages)

Old as (Some) Hills


"The word gay has changed meanings many times over the centuries, both as a standard English word and as a slang term, but it has nearly always had a shady side.
"Two of the less offensive definitions in Eric Partridge's Dictionary of Historical Slang are as abbreviations of gay and hearty, rhyming slang for "party" and gay and frisky for "whisky". That's appropriate, because one 19th century meaning of gay was "slightly drunk".
"The Oxford dictionary gives as one of the 17th century meanings of gay: "Addicted to social pleasures and dissipations; often euphemistic: Of immoral life."
Partridge says gaying instrument was used in the 19th century to mean the male member but this meaning goes back further than that. For instance Capt Francis Grose's Dictionary of Buckish Slang, University Wit and Pickpocket Elequence, which had its second edition in 1811, defines gaying instrument as "penis". Grose supposedly died in Dublin in 1791 so that meaning probably goes back to the mid-1700s."