I'm not sure if this is entirely the right place to ask, but here goes:
Currently, I'm updating an old campaign setting of mine, Etherworld, that is, as the name suggests set entirely in the ethereal plane. Only, this time I'm also writing it up online, over at giantitp.com, the forum where I usually hang out.
My question now is this: I would like to use a few of the things from the Planewalker campaign setting, namely the Control skill and the Nathri race, in my own setting. Would I be allowed to use those, if I credit this site here? Otherwise, I would have to drop those parts, or replace them with other mechanics.
I don't know. It may depend on two main factors:
--What the site's policy has with WotC (for instance, it would seem that DnDwiki, a subpar homebrew site with a server that makes a slug crawling in mollasses in 40f degree weather look expedient-- it does have a few funny entries though such as the "Evil Sucky Thing of Doom", "Hobo", "Club of Kobold Golfing", and this one phobia whose name eludes me *the "breaking the 4th wall" one*)
--How much non-OGL material you use (DnDwiki, for instance, appears to be allowed to mention non-OGL stuff by name so long as a disclaimer is provided)
In other words, if you post the full (or even half) of the stats for a non-OGL 3x monster, you'd likely be in trouble. Quoting a single sentence from a sourcebook is likely okay, though (falls under the terms of Fair Use IIRC)