Cotton has never been a source of food. However, if you would check the labels of the processed foods in you supermarkets, cotton oil has been added to a lot of foods such as peanut butter. Deliberating breeding fruits and vegetables for desirable traits is different.
For example, wild strawberries are very small and wild citrus is bitter; these fruits have been bred for larger size and better taste naturally rather than in a lab by genetic manipulation.
The oil contains no gossypol. I suspect the use of cottonseed oil probably dates back to the Egyptians.
And unless I am not understanding the article correctly, selective breeding and crossing was precisely the technique used to develop the gossypol-free seed variety...not gene splicing.