Mozilla and Opera dropped them because there was a security hole in them that allowed you to access the memory or something like that. Google said that the other two were smoking something and that it doesn't happen in Chrome.EDIT: http://zack0wack0.com/caddock/For Chrome, Mozilla, Safari and (hopefully) Opera. It'll still work for others, just no gradients.
http://zack0wack0.com/wamt.js/examples/box2dphysics.html