usually, you would download both items and do a visual and vertex comparison. if you find that they are indeed the same you post the result to the correct forum. then, you can contact the moderators and ask to have the item removed from the freestuff. If you're not sure about the comparison you could pass the info along to another person and ask them to do the same. in most cases this results in one person slinking off into a corner or if they are real people at least an apology...