Is whey permissible for consumption?

Re: Is whey permissible for consumption?

"Whey or milk plasma is the liquid remaining after milk has been curdled and strained; it is a by-product of cheese or casein making with several commercial uses. Whey is used to produce ricotta and gjetost cheeses and is used to make many other products for human consumption and as an animal feed."
Why would this be Haram?