There are people who don't enjoy building stuff in Java and want an alternative (like Dart).
There are also people who don't want to learn (or like) the existing Android APIs.
Sky opens the door to use Dart on the server side, on the web as well as for highly performant native apps for Android (and eventually for other platforms like iOS).
> Sky opens the door to use Dart on the server side, on the web as well as for highly performant native apps for Android (and eventually for other platforms like iOS).
What's wrong with using GWT and J2ObjC other than the fact that there are people who don't enjoy building stuff in Java?
I don't see anything 'wrong' with GWT, just as there is nothing inherently wrong with writing iOS apps using Ruby (http://www.rubymotion.com/).
For example the Inbox team did a fantastic job re bringing a great user experience to multiple platforms and I guess they were glad that they could use one language throughout instead of having to jump between various tools and idioms (see http://gmailblog.blogspot.com/2014/11/going-under-hood-of-in...).
It's just that like you mentioned people do have different preferences when it comes to languages/tools/ecosystems. That's all.
There are people building web services using PHP, Ruby, Python, Java, Haskell, Elixir, Erlang, Go, C++, JavaScript, Dart. Why not also have this choice on mobile?
They don't dislike the language (some of them even worked on the JVM's major implementation, HotSpot).
They are building a competing VM, DartVM.
Because of the way Dart (and its VM, built for its needs) was designed, they believe they can eventually outperform Java on the JVM, all the while providing a fully dynamic programming language, because of smart runtime optimizations.
If they win this bet, they'll have made an acceptable replacement for the way Android apps are built. Then, things would get inversed, and developers wishing to keep using Java would use a Java-to-Dart compiler (instead of a Java-to-JVM bytecode one).
Sky opens the door to use Dart on the server side, on the web as well as for highly performant native apps for Android (and eventually for other platforms like iOS).