Shalom u Bracha
Does Chalav Akum requires Kashering the utensils to those that are makpid on Chalav Yisrael?
A person that cooked Chalav Akum in his pot etc. has to kasher the pot, as the Rema writes in Y:D 115-1, and there is no such thing as not being makpid on Chalav Yisroel, as it is something that chazal said we all have to observe. What you most probably are referring to is the widely known heter of R’ Moshe zt”l that in the United States and other developed countries, that have an organized governmental supervision on the milk farms and it is illegal to add any non kosher milk to the cows milk, that it is considered clear that nothing was added. This is called chalav stam.
Although R’ Moshe says that it is not forbidden to drink, he does say that it is preferred not to, and that this is how he acts. Other poskim say that it is indeed not kosher. Regarding the utensils for someone who doesn’t drink Chalav Stam, it really depends on the degree of why you dont drink it. If you don’t drink it because you want to be machmir, like R’ Moshe says is the correct thing to do, even though essentially it is not “trief”, then you would not have to kasher the utensils. However if the reason you don’t drink it is because you hold like the poskim that say that it is like real Chalav Akum then you would have to kasher the utensils. Many people in the United states, although they are makpid not to drink Chalav Stam, but they are not makpoid to the degree that the utensils have to be kashered.
Igros Moshe Y:D 1 47-49, 2-35, 3-17, that according do those who hold that it is definitely assur that they should kasher their utensils, Shulchan Halevi 1- Chapter 22 5-1,