I think sections 1 (g) and 2 of the license are the operative ones. Section 1 (g) says:
g) "Use", "Used" or "Using" means to use, Distribute, copy, edit, format, modify, translate and otherwise create Derivative Material of Open Game Content.
Section 2 then uses the term "Use" as just defined:
2. The License: This License applies to any Open Game Content that contains a notice indicating that the Open Game Content may only be Used under and in terms of this License. You must affix such a notice to any Open Game Content that you Use. No terms may be added to or subtracted from this License except as described by the License itself. No other terms or conditions may be applied to any Open Game Content distributed using this License.
So basically, if you create content derived from OGC, you are Using the OGC you derived from. If you Use any OGC, you have to affix the notice, and affixing the notice means the license applies to the content you affix it to (which means the content you derived from the OGC you Used).
This is just my interpretation, of course, and IANAL.