Interesting article. I found the following quite illuminating:

While I was compiling this list, I thought hard about putting Android on. It’s hard to argue that Android is unimportant in 2011, isn’t it? Absolutely. It’s also, unfortunately, hard to make a strong case for Android as an open source project.

Sure, Google lobs some source over the wall when it gets around to it – but Android development happens mostly behind closed doors. There’s little opportunity for the millions of Android fans and potential hackers around the world to influence Android development unless they happen to work for Google or one of its partner companies.

It’s great that Google releases the code, but it’s more of a “source open” project than an open source project.

This is why I laugh at Android fans when they point out how “closed” the iOS platform is.