Update#3: The code redemption is over.
Update#2: More codes were updated to the Reddit link.
Update#1: More codes were added to the Reddit link and some had expired. There is also an official statement from the developer that any abuse of the codes will result in banning.
Source: Reddit thread
It seems like quite a number of websites are getting these free codes to redeem packs. You do not need to type them in caps or include the dashes and they redeem unlocked packs so I intend to keep them for trading. The codes expires on 10 October 2014.