How reliable are the poses?
Do they give you what you want?
Are they exaggerated? Do they go beyond natural human limitations?
Would your wardrobe comply with the poses?

My take on it, use canned poses as a starting point and modify it until you attain something you feel is unique for your scene. Especially, if you totally suck at posing. Ethical? I think it's perfectly fine to buy and use, that's what the product is for.