Help with copyright: what constitutes a 'setting'?

[thefantodayhtml]

I’m in the planning phase for a demiplane that I want to be compatible with (and accessible from) the Forgotten Realms setting, but would also be geared toward campaigns set (or at least starting) within the world itself. It would require the core rulebooks to be played, but could potentially be played with only those rulebooks without any need for Realms specific content. Would this be considered using the Forgotten Realms setting (or no setting) as per Dungeon Master’s Guild copyright rules, or would it be classified as a setting in and of itself and have to use OGL? I'm mainly asking becuase if there are any potential legal complications, I would like to know now so that I can adjust things acordingly without having to worry about having to rewrite large parts of the setting.
edit: In responce to the concerns of Xuc Xac and PhoenixPhyre, I would like to clarify that my queston is not about any section of copyright law itself, but the Dungeons Masters' Guild policy with regard to settings, and whether what I am doing would be a original setting by their standards and thus violate their policy.

[Xuc Xac]

I'd recommend doing some research into the difference between copyright and trademark (and patent, while you're at it), then come back and ask the question more clearly (if you even still have a question after understanding the difference).

[PhoenixPhyre]

As a note, legal advice (which is what you're asking) is forbidden on this forum.

[thefantodayhtml]

I'd recommend doing some research into the difference between copyright and trademark (and patent, while you're at it), then come back and ask the question more clearly (if you even still have a question after understanding the difference).

I'll do that.

As a note, legal advice (which is what you're asking) is forbidden on this forum.

Right. I think that I may have misinterpreted that part of the rules somewhat.