To developing countries only. I didn't see how a country is deemed no longer developing, so it makes me think it's just the classic pusher tactic: the first crop is free.

Once a developing country's economy has become entangled with the crop, start charging rent.

They actually licensed it to low-income, food-deficit countries as defined by the FAO, which means that countries have to both be below a minimum GDP per capita and grow less calories of food than required to feed their population. (The pilot project was in the Philippines, which has since been retroactively removed from the list due to a re-estimation of their GDP.) Most of those countries can't grow rice for climate reasons. Worse, the estimates of its usefulness assume that a rather large proportion of people's calories come from golden rice, which obviously isn't possible - and it's of questionable effectiveness even then.

The Phillipine government has since largely solved their vitamin A deficiency problem through a lower-tech and cheaper approach: vitamin supplements.

The IMF typically determines the developing country status based on HDI, and when countries graduate to developed status.