Who's Dan?
If someone sells or gifts me a book that contains material that was licensed to the publisher under the OGL, I get the same rights to use the material as anyone else does who purchases any book: in the US that would be fair use, I think, which I would assume must be informed by the context.
You get more than that.
"10. Copy of this License: You MUST include a copy of this License with every copy of the Open Game Content You Distribute."
And, that copy of the license includes the same offer and acceptance previously noted, so the license is self perpetuating. Every use of the license includes an offer to use the license.
Just in case you haven't reviewed the license itself recently, you can find a copy of it here: Open Game License v1.0a