EA really wants you to install their Origin service. And to make that happen, it's offering a free game every month. Last month it was Dead Space, and now, it's Battlefield 1942. All you have to do is log in, and download it.
It's already been about a year and a half since it last offered BF1942 for free, so why not? Might as well grab it for free. In fact, it looks like you can still grab Dead Space for free, right up until the 9th of May. Happy Easter!