Nope. You're stuck with the GOG key, I recommend you try to appreciate it.

And welcome to GOG.

Welcome to GOG, kick back and enjoy.

Why would you want a game with DRM over one without? Pardon my French but that sounds a little Bass Ackwards to me.

*free*

No, it won't be possible. The reason being that GOG doesn't distribute steam keys, and that GOG is part of CDProjekt Red, the same devs that does the witcher series.

The good thing though is that GOG is a great site, entirely drm-free. You can use the occasion to browse the catalogue and see if there is something to your fancy :)

You'll likely catch some heat for making a post of this like with so many similar popping up lately.
To answer the question there isn't any official way of getting a steam key from GOG.

You could chance getting ripped off by trying a swap on the Steam forums or other trading site, but I'd urge you to just redeem it here and add it to Steam as a NonSteam game if you want to keep all your games in one launcher.

The nice thing about GOG and other DRM free places is that even in the unlikely event they go under, as long as you still have your installer, you can still play the games you bought.
If the same were to happen to Steam somehow, it's less than clear if you could still gain access.

GOG is also working on their Galaxy client, which should bring automatic updates to the game if that is a concern for you.

Thank you for your replay

One main reason is that because i want to have all of my games in one place, i have both the witcher & the witcher 2 in my steam library so it would be nice to have the third one also there.

Actually that does make sense. Still I recommend you take a look around here; it is a very amiable site and the forum member are great, well except for that guy, and that one, and that dude over there. And that guy over there is really nice but he smells like tuna fish so keep your distance.

I'm pretty sure you can redeam witcher 1 & 2 from steam on GOG. That would let you have all three here, mission complete.

I showered this month, the smell should be minimal

I guess i started to like GOG

The first reason is that i didn't expect this much answers in a very short period of time! Great community here!

The second reason is that i have now more clear idea about what DRM Free is.

The third reason is that why not give it a try?!

Does GOG have achievements?

Thank you all for your participation, and for the helpful info you have provided.

At the moment not. But an optional client (GOG galaxy) is being developed at the moment and this client will have achievements.

Client in development?

Thanks for the info.

It is at the moment in alpha testing phase:
http://www.gog.com/forum/general/gog_galaxy_client_closed_alpha/post1

But one of the gog staff already meantioned that the beta should start in a few weeks.

This is nice.