Just like Microsoft
Now that you have to pony up for PlayStation Plus to play online on the PS4, it seems as if Sony is packing in free trials with various multiplayer games. Similar to how Microsoft packaged them on the 360, a few of the games I've opened so far like FIFA 14 and Assassin's Creed IV have had vouchers available, so this appears to be a thing going forward.
They're a little less necessary on the PS4 however, as all accounts on the system can benefit from a Plus membership (the Xbox One does the same thing for Gold) -- as opposed to the 360, where each account had a separate Gold status. But still, free is always good.
By the way, that code in the header is live and ready to be taken if you want it!