I don't know if you've tried downloading any of the OGL stuff, but I think it's restricted to the material in those packages (I don't think Lolth is in there) and for gaming purposes only.
Basically, you can create a DnD clone pretty easy anyway and there isn't much they can legally do about it, so they thought, "okay, you can use our system, just give us a little credit here will ya?" It's smart, because it allows third parties to expand their game in new ways with fairly compatible material and that keeps it interesting to fans. But the OGL statement demands that you recommend people get the official d20 books, so it is a calculated buisness decision. I don't think it is an open license on their characters and their universe, because that does not necessarily benefit them in any way, and characters are much more ownable than game rules. I think most of the creatures included in the OGL materials are pretty much just generic models of the creatures most common to DnD campaigns, and that is probably done because they can't claim exclusive ownership over dwarves and elves, might as well keep the games consistent and compatible.
Personally, excep for major characters like those in Dragonlance and Forgotten Realms, I don't think there is anything terribly unique about most of the characters/creatures in DnD. Most are modeled after characters in real world mythology, and if you start mining into that, you will find THOUSANDS of creatures and demons to pit your heroes against. Name anything in DnD and there is probably a PD mythological source for it (I don't know what Lolth is based on, but there were dark elves who lived underground in mythology).