Hmmm, what is it, and how do I know I have it on my GOG edition here?

Well, did you back it through kickstarter in the first place? If so you should get it. I guess it's either a patch, or a code you type in like in D:OS, since having two completely different gamesfiles would be kinda weird, but you never know.

It is Kickstarter-exclusive, it is a code we provide through the Ranger Center which unlocks the "Southwestern Folklore" skill, which has no gameplay effects but gives some extra descriptive text

yep, and i found it really nice :)

It isn't a separate DLC or anything like that, but actually a very well-hidden easter egg - that backers are told how to uncover on the Ranger Center site. The instructions (which I also missed myself) are written on the page you retrieved your GOG code from.

At the risk of being lynched by 61,290 angry kickstarter backers - the instructions have already been posted over at NeoGAF.

Have a character read the book you're given to gain +10 ranks in Southern Folklore.

Not sure whether I'll use it myself for my first playthrough; I don't want any spoilers or added sillyness!

Thank you! As a backer myself, if I were able to remember my password for the website, I could have found this out again. Lacking that datum, yours was the first spoiler I found which told me what I already should have known.

Nah, that is why the skill was not relevant.
We know everyone want to share the things they got (even if that destroy your own funded company)

By the way, there is no spoilers with that skill (At least you want to play Wasteland 1 later)