Why resellers? Is a shop that sells the boxed version a reseller, for example?

I just did a quick check, I haven´t found anything about TW3 and Namco-Bandai as distributor or similar.

All info I found is that CDP made it all by themselves. Please correct me if I am wrong.

Yes on http://buy.thewitcher.com/?lang=en&country=EN it is at the bottom mentioned, but not anywhere as reseller/retail or whatsoever.

So I don´t think that the other shops got the keys from them.

Namco-Bandai is the game's European/Australian physical publisher (also shown at the bottom-right corner of the game's box on the CD Keys site). A possible scenario is that CD Keys bought a bunch of retail Witcher 3 discs from Namco-Bandai and since each of the physical versions of Witcher 3 contains a GOG code, they are able to just sell the GOG codes directly through their site.

Again, GOG does not have resellers. GOG sells gift codes, which are not for resale. GOG can also provide developers with bonus codes, that the developers can then use. A developer (like CDPR) may choose to give said codes with the retail version, or through Humble Bundle, though those are not GOG gift codes. Not sure that GOG can dictate terms to developers on how they use the bonus codes, but they can refuse to provide them with said codes.

hmmmm....

Ok I believe you ;) Aaaaan I just checked on bandai ;) see below

BUT

When I checked on https://www.bandainamcoent.eu/product/the-witcher-3-wild-hunt/pc

It is ONLY referring too thewitcher homepage, where we are back to the beginning. I also checked with another game and there was a direct link where to buy..
Strange......
So IMHO your scenario would be ruled out, unless they only do business with big companies (but there again see my comment before)

Do you know where I base my assumptions? On GreenManGaming's Witcher 3 page (see image below). Thus, I imagine a similar case with CD Keys. Besides, I'm not 100% sure that Namco-Bandai is obligated to mention every single seller they are doing business with.

Yes, they are the publisher of the game. Doesn't mean GMG has the keys from them. It is just a piece of factual information about them.

hmmmm....
I think you missed my point (might have been me ;) )

For other games, Namco is showing directly a link where to buy (i.e. steam), but for TW3 it is just pointing to the CDP the witcher side and this in turn directs you to the link above.

So, why do they handle TW3 different? I could understand this (only), if they would be the legal point of contact for boxed versions.

Just tested a few more:

https://www.bandainamcoent.eu/product/f1-2014/pc

even worse then TW3, you can´t buy it at all ;)

So it might be as you said, just laziness from their side ;) But still strange though

GOG and Steam mention CDPR as the publisher. Why not GMG?

They are misinformed? Stupid? I don't know.

I don't know the correct english word.
Affiliates? Third parties who offer bonus codes?
GOG should say who is safe\unsafe to trust.

Developers/Publishers. GOG only provides codes to them. So GMG (example) may be a legitimate seller for Defender's Quest, but not for The Witcher 3.

Edit: They sometime offer individuals codes as well, mostly through contests and promotions. Those will be unlikely to be sold by a store though, but may be found in a marketplace.

If cdkeys is indeed legal then surely there is no reason to buy somewhere else. After all you anyway get exactly the same product - so why paying more than is necessary unless you want to support CDP in which case one should buy here. In order to verify the legality of cdkeys or other resellers it might be sufficient to ask CDP for confirmation.

Steam Is going to be in some SERIOUS shit then!

http://store.steampowered.com/app/292030/

I'm curious about Nuuvem. They had the Witcher games discounted deeply during their recent sale with GOG keys.