Android is far from open source, both practically and in spirit

Android: the free-ish mobile platform | Jethro Carr

"Whilst I’m a fan of the platform overall, I’m encountering more and more issues every day with the fact that Android is being positioned as the poster child of open source in the mobile space (with other alternatives like Meego and WebOS way behind in terms of market share and consumer awareness), yet Android is only partially open source, still relying on large proprietary chunks."

See also the Open Governance Index report.