Well, I think our different understanding of the way the games are licensed is what makes us having different opinions on the way we "should" use said license(s).

The user agreement terms are not the same on the DRM-free version and the Steam one, that’s what makes me think of two licenses where you see only one. In my case this view is strengthened by the fact that I accept one set of licensing terms and not the other one.

Selling the key is technically possible. So goes for trading the key, all very much possible.

It's mostly up to the developers who put up the games in question and their stance on DRM-free. How many people are known to use this trick? Those who wanted the Steam version of the game forgot about the DRM-free downloads and all. I'm saying it's no significant enough unless you're an indie developer called Jonathan Blow, or a group who are really concerned with money flow like Butterscotch Shenanigans. Neither that, or that, is abuse. When I buy a Humble Bundle with both steam keys and DRM-free, I'm entitled to both as separate entities with separate laws. For one, Humble Bundle technically and legally allows me to own the DRM-free download, and send a specific key to another user. Why do I say this? Suppose I bought for myself the current indie bundle. Going into the Humble Bundle library, and limiting my view to "Windows" games, I'd see Outlast at the bottom, downloadable. Limiting my view to "Steam" games, I can see that very same Outlast key, which I can activate for myself (what a waste) or send to a friend. So basically...I'm entitled to two copies, how I gift or send that Steam key is certainly none of their business once I see the code itself. I did it before with Deadlight. I still have the DRM-free download for it, and a friend got the Steam key, happily playing it.

So, this is not abuse. They could have erased the DRM-free Deadlight after sending the Steam key, but they didn't. I can play the game, and my friend can. It's in their system since the very beginning.

While I agree on the rest on your post, this point made me jump from my chair ;)
Of course it is *technically* possible, but it is explicitely forbidden in the user agreement.

The dicussion here is not about what is possible (nearly anything), but more about what is/isn’t in contradiction with Humble rules.

At the same time, it is technically possible. By allowing me to see the code, I can do whatever with it. This rule shouldn't even be there if they can't enforce it in some way. After all, they sold me a freely usable key and download. By the moment they gave me the key, my relationship with Humble Bundle is over, and then it's time to move on to the Steam relationship part. That's being a key reseller for you.

Technically you could download a game from humble or GOG and distribute the installer to everyone you know.
That doesn't mean it would be right to do so.

The DRM-free download is non-transferrable, so ideally, the last stop for that download's distribution stops at whoever who will redeem the DRM-free download. The Steam keys however are transferrable, which means that I can distribute it however I wish, knowing that once it's activated, it is no longer available for distribution, and thus it's the end of the line for it.

This is not insofar comparable to piracy in the sense you brought up, as Humble Bundle allows me to gift the Steam key with even a proper gift button and all, and YET still keep the access to my DRM-free download. That's the story with my Deadlight. The conclusion is, Humble Bundle allows me to deal with the Steam key as a separate entity (from the DRM-free download entity), and as such, I'm free to distribute the Steam key without any legal implications whatsoever.

I do agree that it should be allowed to give the Steam key to anyone. I disagree with selling it.
Even if it's legal it doesn't feel right. Of course you are free to do as you please. ;)
If Humble disagrees they could always sell them seperately I guess.

Basically as long as I can get my DRM-free games in the end, I'm happy whenever Humble Bundle shows me a respectable DRM-free bundle. I don't mind if I lose out on the Steam keys.

Actually, on this point you are simply wrong. Practically and legally. Two reasons.

1) as PaterAlf have already said - when you buy a bundle you buy 1 license, not 2 (or more....). So not going over this again.

2) Steam key != game license. This can not be stressed enough, so I will say it again: A steam key is not a game license. A steam key can be seen is an agreement between you and steam to make use of the steam services for your license, it is not a license in itself. The license (in this case) you buy from Humble, and it is (as per point 1) only 1 license. There is really no way around this, it is what it is. Where ever you buy a game from, which comes with a steam key, the vendor sell you 2 things - the game license and the steam 'allowance' to use their services. Legally, these are two separate entities.
See my point above about Steam keys and game licenses - what you transfer is basically the right to use Steam to manage your game, you do not transfer the license. Therefore, if you want to be very legal, the only way you can keep a DRM free game, and give away the steam key, is if the person you give it to already own a license of the game, but not on steam... if that makes any sense.

On principle, I agree with you... then they added the gift buttons that let you gift the steam key and keep the download. I'm conflicted now, because it still seems wrong to me but Humble seem to actively encourage it. Well no, a better explanation would be because that would stop legit users from having both a DRM-free download AND a Steam key which is something that Humble wants to provide. Your logic is like saying that people who don't put DRM on their games want it to be pirated.

An interesting thing here is that when people have this kind of question, they don't think of contacting Humble or the devs who provide the games for the bundles (and are really the ones whose opinion matters here) but post it to a web forum. Obviously they want validation, not an answer.

there is a bit of cognitive dissonance there, yes... Parts of me wish they would have a single "gift" button, which takes away both DRM free and Steam key when clicked, and a redeem button which gives you the DRM free installer and the Steam key (but no longer gift-able). That would have been the best situation. However, this is not we have, and I bet if they did implement this there would be tears and rattling of sabers.

edit - I think groupees have this system?

That looks far from what Humble Bundle had in mind when they put in the gifting system. But clearly, what they intended to the very legal detail is that you can keep the DRM-free download, but the Steam key is something you either wastefully eat or send it over to a friend via the gifting method.

indeed... and see which post was marked as the right answer....
no, the point is that they give you choice. That is all. there is nothing lost or gained by using or not using the steam key. This is bits and bytes we are talking about here, there is nothing being lost or rotting or wasted. All it is is an entry in a database which will later be deleted.