i would strongly advise not allowing this magazine to have Copyright on the material. There is absolutely no need for them to have it. Many gaming magazines provide freeware on their included discs but do not own the copyright, simply go out and buy a copy of PC Gamer and you will see.
SO the fact that they are asking for copyright should worry you a great deal. You will effectively be signing over the interllectual property rights of your work and they will be free to do as they wish with it.
