I purchased Humble Bundle Weekly: Gamepedia Presented by Curse.

The bundle includes Curse Premium 30-Day Subscription.
According to Humble Bundle and Curse, Curse Premium offers many other benefits including: "One free game from GOG.com"

But I cannot receive it, so I contact Curse support.
Curse said: "We realize that the GOG code isn't working due to an expiration issue. Since we're not able to revive these codes, the only option we have is to give you an additional Curse Premium subscription instead."

According to Announcement: Curse.com Partnership (http://www.gog.com/news/announcement_partnership_with_cursecom)
The partnership offer remains valid at least until December 31, 2014.

So,
Why cant I receive my free GOG game???

If you click on this link to the official Curse.com announcement, and scroll down to the bottom where the comments are, the offer was announced on 13 December of last year. But by the 28th, they had run out of keys/ codes. So, perhaps, given that 23,988 Humble Bundles have been sold altogether, that's what has happened again, rather than the codes expiring. They didn't anticipate demand to be so high.
Maybe, and I emphasise, maybe, GOG will give them new codes next week. It depends on who's balking at the number of games being given away for free, Curse or GOG.
Curse are possibly finding out that not many people are sticking with them once they've received their code. I know I clicked on "Do not renew" immediately after I got my game, and it turns out you didn't even have to install their client to get the code.

Well if Curse did run out of keys, which seems likely given the huge number of people who bought that Humble Bundle, it seems like GOG isn't going to give new keys.

Humble completely edited out the text that said you get a free GOG game with the month of Curse (it still can be found in Google cache at present http://webcache.googleusercontent.com/search?q=cache:RHhKLy9526EJ:blog.humblebundle.com/post/91370696625/game-encyclopedia-gamepedia-its-the-humble-weekly+&cd=3&hl=en&ct=clnk&gl=us ) and Curse updated their page to say that the offer, which was supposed to last at least until the end of the year, has expired. http://www.curse.com/news/curse/49289-curse-premium-membership-now-includes-a-free-game

*Edit: Since the Google cache has been updated, I suspect by request, here's a screengrab of what the humble page originally said: http://s17.postimg.org/9hhhgcjan/Screen_Shot_2014_07_12_at_2_24_27_PM.png

Thanks for mentioning this. I was going to up my purchase on payday to include that tier to get the GOG game. Now I can see there is no point and that really should have been clarified or changed before the bundle went live as it is definitely false advertising.

Some people still got their GOG game from the Humble Bundle (here and here, for example) so it seems it was not false at the time the bundle started. The mention of a GOG game has been removed now.

Thanks for posting this. Since the offer is valid until December 31, 2014, you should have gotten your game no matter what. Something is not right here. The "expiration issue" looks like a cheap attempt at not fulfilling their promises. I think we need a comment from one of the blues.

Basically.

My hunch is that Curse was somehow completely ignorant of the fact that Humble Bundles sell tens of thousands of copies and that of those tens of thousands of people a good portion of them would of course redeem a free offer while they only had a finite amount of keys and GOG would not give more.

An alternate theory might be that Curse was freaking out about handing out arguably their biggest draw to subscribe to what amounted to a bunch of bundle freeloaders and 'expired' the offer but may magically 'unexpire' it when the bundle is done (or a month later after all those people have their free trial subs run out).

Regardless, the way the whole thing was handled was quite shady and both Humble and Curse tried to hide what happened by creating a revisionist history where the offer was never made (Humble) or expired much sooner than it was supposed to (Curse) instead of just being honest and commenting that the promotion ended early with reasons why that happened.

People that have complained to curse have gotten additional months of premium

Dont know it that makes up for the game but its something.

Maybe you can explain what's the use of Curse in the first place.
:-)

"Therefore, instead of thinking of swearing as uniformly harmful or morally wrong, more meaningful information about swearing can be obtained by asking what communication goals swearing achieves. Swear words can achieve a number of outcomes, as when used positively for joking or storytelling, stress management, fitting in with the crowd, or as a substitute for physical aggression. Recent work by Stephens et al. even shows that swearing is associated with enhanced pain tolerance. This finding suggests swearing has a cathartic effect, which many of us may have personally experienced in frustration or in response to pain. Despite this empirical evidence, the positive consequences of swearing are commonly disregarded in the media." From the science of swearing :)

:D
Great and informative answer.

I just find it a bit shady, the way all of this has been swept under the rug and silently deleted without barely any announcement from anyone at all :/

Myth Confirmed by the Mythbusters. FYI

And if my friend from school says it's true, then it is definitely confirmed as she was always pretty brainy :)

Nothing is really lost in the internet.

As you can see they posted it at the 22nd January

"Today Curse and GOG.com announced a new partnership which gives all Curse Premium Members their choice of one of GOG's most popular titles - FREE! This offer applies to all current Premium members and all new Premium subscriptions purchased between now and December 31, 2014. "

https://web.archive.org/web/20140122205407/http://www.curse.com/news/curse/49289-curse-premium-membership-now-includes-a-free-game