ChromeOS is pretty much closed. You don't have a say on what goes in, you don't have a say on what they're going to do with it, you don't have a say if they want to fully close most of it.
In fact, you can only see the parts they let you see (in ChromiumOS), and that is the only difference with Apple or Microsoft (albeit arguyably, Apple also open sources it's kernel)
This is not true, there isn't much in ChromeOS that's not in ChromiumOS. You can file bugs on crbug.com and they are positive of most requests. And of course you can fork at any time; Chromium is developed in the open.
