It's a fine distinction (and please feel free to correct me, anyone, if I'm wrong here) - basically, anything you write using OGL mechanics is "closed content," meaning that someone who wants to use it should ask you (meaning it's strongly suggested, but not required, as I mentioned earlier). WotC, as the originator of the OGL, doesn't have to ask - they have savoire faire to take anything created using the OGL and plop it into their books - but it's generally considered nicer to ask first. One of us, however, would have to ask WotC to use, say, some feats from one of the splatbooks, because it's all closed content (they are, however, quite gracious about granting access to most material if you ask nicely).