where are you reading that the OS is not open source?
there is a difference between the OS, the applications that run on that OS, and the documents that you use those applications to read
the OS that's been deployed is open source (like any other purchasers, countries can load other operating systems on the devices after they buy them)
the documents that are provided are all provided under licenses that allow for free distribution, but not all documents are distributed under licenses that allow them to be modified.
in my opinion this is not a bad thing. not all documents should be modified. One particular case that I think of is the Internet RFC documents. they can be freely distributed, annotated, etc, but you cannot modify the document. I see this as a good thing. standards (and reference) documents being distributed unmodified is good.
having other things that can be modified is also good, but don't confuse the two.