Here is a great analysis of the Android ecosystem as it is maintained by Google. Android is slowly but surely becoming a walled garden, although, the walls are farther away and hence less visible than in IOS.
http://arstechnica.com/gadgets/2013/10/googles-iron-grip-on-android-controlling-open-source-by-any-means-necessary/
http://arstechnica.com/gadgets/2013/10/googles-iron-grip-on-android-controlling-open-source-by-any-means-necessary/
