As I understand it, the maker has always been open about the recipe. I've never tried making my own Sriracha, but I've made several other pepper sauces and found them easy and delicious.
Supposedly the Huy Fong Inc version is no where near true Siracha and most people in Thailand don’t think it’s good.
Sriracha didn’t exist before the (Vietnamese-) American sauce.
Flying Goose is the way to go, they are made in Thailand and come in a variety of different tastes including Mayo, extra garlic and extra hot "Blackout".