You're confusing Android with AOSP. "Android" is like "UNIX", it's more of an definition and API but not a specific product. Just like you have Solaris, IRIX, AIX, etc that are all UNIX because they satisfy the UNIX definitions; likewise AOSP, Sense, Blur etc are kinds of Android. I assume all known Android variants are derived from AOSP, but they don't have to be.
