Yes, it is edible although it's not as creamy and pleasant as the cheese itself. I have eaten it many times especially when I've used it for a cheese tray or charcuterie board. But for the best, creamiest results for mac and cheese I trim it off before grating it. The brown part, or the rind, on Smoked Gouda, doesn't melt as smoothly as the cheese itself. Generally, cheese rinds are perfectly fine to eat as long as they aren't made of wax or cloth. And some rinds are so thick and hard they just aren't palatable.