Dart at this point is being directed by Google, but it is totally open source. So if Google decided they wanted to stop working on it, you would still be free to do what you'd like with it.
The Dart code[1], which includes the VM, dart2js, editor, analyzer, and all libraries are under new BSD license. The entire contents of the dartlang.org website are even on Github[2] under Creative Commons, so you can submit pull requests to have any page on the website updated.
While it's direction is being decided by Google, they are taking a lot of input from the community via the mailing lists and bug submissions. Though, it is not driven by committee like EMCAScript is, I'm ok with that for now. I believe when Dart was originally launched they said they would consider submitting the language as an ISO standard once it has become more stable, which may still happen.