The Dart source code is BSD licensed, available on Google Code (hmm... I wonder when Google Code will get shut down...)
One of the contention points in the WebKit/Blink split was support for non-JS languages. Chrome (and Opera, Google's bitch) will, I suppose, support it, but Firefox, Safari and IE? Then again, IE used to support VBScript and PerlScript back in the day, so maybe Google could do an IE/Dart plugin.
Being killed off is better than the alternative -- forced integration with google+. Will they require you to login to google+ to run the javascript transpiler? Will they auto-post your error log to your google+ page? Will they remove the "+" operator (like they did with search)? Who knows!
"Gravitation cannot be held responsible for people falling in love." -- Albert Einstein