Grargar: Just a heads up, but tomorrow, the free stuff should be vanishing from your accounts, so make sure to backup your installer and/or redeem your Steam key.
DProject: Pretty sure they mean that the game will be available for free for a limited time, after that it will no longer be free but it will still stay on your account though if you grabbed it.
Grargar: I doubt it, as it wouldn't make sense to display this notice in your account. Besides, the game was available for free till 31 August. This is different.
Yeah, I'm with Grargar on that the way it is explained it will be removed from your Humble account, but why they are doing this I don't know, especially considering that the Steam key, once redeemed, won't get taken away, so you still own the game. Therefore what's the point in taking away the DRM free version? Seems very strange, so I can only guess it is the dev and/or publisher insisting on it.