Just curious if there's any way to get a Steam key with the GoG version of the game? I'd like to write a Steam review and other features.

Nope. When you buy a game from GOG you don't receive a key because the games are DRM-free. If you want full Steam support you will need to purchase a Steam licence for TW3.

That argument doesn't really say anything in itself when in the a lot of other non-Steam storefronts you tend to get both DRM-Free *and* a Steam key for games. (not the Witcher 3 obviously)

Sure it does; it provided an answer for the question asked, there were no fallacies or exaggerations, everything was factual and kept short and simple.

Policies held by other key shops are irrelevant to the OP's quesiton.

I disagree, I think it's important to take into account the average consumer expectation when it comes to questions like this. You could've left the DRM-Free part out and the answer would've been shorter and simpler and just as useful.

Saying 'GOG doesn't give Steam keys because what they sell is DRM-Free' is a confusing statement to people who are accustomed to stores having no issue giving both for a single purchase. At best it says 'They don't give Steam keys because they don't'. At the very least one should argue then that it's because GOG is a stickler about the DRM-Free stance so they can't endorse giving out keys for a platform that has DRM. That makes sense. The games 'being DRM-Free' is not a reason in itself.

I didn't say Steam keys aren't provided because GOG is DRM-free. I simply stated they don't provide keys [in general] because they are a DRM-free store, then explained that in order to get full Steam support you need to purchase a Steam license. Again, all true and the OP is aware that they will not receive a Steam key from GOG; exactly what they wanted to know in the first place.