OneNote is part of the Office "family," but at
this point does not share all the functionality of the older siblings.
I'm sure parts of the codebase are shared with / borrowed from Office but
I'm struggling to see how end users are supposed to view OneNote as part of
Office given that many of the fundamental features e.g. drawing tools,
hyperlinks, are currently missing and OneNote itself is sold separately -
regardless of which version of Office you buy.
OneNote is more like the family dog than one of the siblings
P.S. I love OneNote, use it daily and can't wait for the next release(s).