Think of cooking. You enjoy a dish from a Chinese restaurant so much that you decide to make it at home. You only have a vague idea of the ingredients, so it took you few years of trial-and-errors until you finally got the dish to look and taste exactly the same.Did the Xinhua article explain what "self-developed" means? Did the project team designed it from scratch, or did it modify a foreign turboshaft and called it self-developed?
Is it a copy? Yes. Is it self-developed? Yes. The two terms are not mutually exclusive.