Within the context of the OGL, the relevant clause seems to be 5: "If You are contributing original material as Open Game Content, You represent that Your Contributions are Your original creation and/or You have sufficient rights to grant the rights conveyed by this License."
There's two angles to that. First is that the sentence begins with an "If". You can, of course, use non-original material if it's OGC.
Secondly, "original material" relates to the expression, not to the idea. The idea of rolling a dice isn't original, but the words WotC use in the 4E Player's Handbook to explain how you roll a dice are original. If you explain in your book how to roll a dice, you can say the same thing, but you have to use your words, not WotC's.
So the idea of AEDU isn't a problem. It's just the words you use to describe it. Ideas (or more properly, inventions - products or processes) are covered by patent law, not copyright law. For example, WotC can challenge companies over cloning M:tG because they have been granted a patent covering certain specific original processes in the game (I'm not sure which - I don't play it).
But that's a whole different kettle of fish to what we're discussing. Patent law and the OGL don't intersect anywhere.