AoSP (aokp,cm9,codename) are built from Google's source repos. This is also where 4.0.4 is from, its the next update for ICS with many bug fixes including video(Netflix,YouTube) and video in browser working, as well as many other numerous bug fixes within the code. The manufacturers have 4.0.3 have already put alot of work into it and will continue using it as their base until they have the initial release out then will start merging 4.0.4 into their upstream, to be included I'm the next round of OTA's. Anything 4.0.4 is AOSP meaning pure android no 3rd party manufacturer UI such as TouchWiz(Samsung),Blur(Motorola),or Sense(HTC). AOSP is what ships on the Nexus line, also called the Google experience.
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