The offer hasn't actually begun yet. According to the Terms and Conditions it starts on 13 July. http://www.dailymail.co.uk/home/prmts/article-2138468/A-FREE-month-family--friends-Railcard-.htmlI believe the offer ended.
That is for the free two month Railcard. The OP asked about the half price Railcard which is only available to those who have the code which was sent out with the free ''trial'' Railcard.