Open Source alternative to Java/Flash/Silverlight

dgym writes: Having applications that can be deployed on the net and run either in a browser or from a standalone player is an old idea, but still not one that has been done really well.
Java is one solution, but for various reasons hasn't attained ubiquity. Now that it is being open sourced it might find itself on more platforms, but it still may be too big for some devices, and too slow to start up to not be annoying.
Flash is geared towards video and animation, but can also lend itself to RIAs and it is certainly a very popular plugin. However, like any closed standard, it is only available on the platforms Adobe decide to support.
Silverlight might be a better platform for RIAs from a technical perspective, but is otherwise in the same position as Flash (only with even fewer platforms).

So why are there so many poor choices for such a simple problem? After all the requirements for developing applications are rather low:

• A sand boxed virtual machine for running client side code.
• A means to display information, i.e. graphics drawing primitives.
• Event handling for user input.
• Networking back to the originating server.

Can we not have an open standard for these, and open source plugins implementing it? The "virtual machine" could either be defined in terms of a language (e.g. ECMAScript), or be a true byte code engine such as Parrot or Mono. The graphics are straight forward, and using a cross platform library such as Cairo would help make these plugins extremely portable. Networking is almost trivial, although being able to make HTTP requests using the browser's proxy settings would be an important consideration.

The need is there, where is the open standard?