Interesting, but who is responsible for the compilation? The plugin developer? The app developer? The realms approach feels a bit cleaner to me... I would think it's also easier to debug than trying to debug compiled code.
The host page must control the compilation to ensure the safety of its data. The compiled code is still JavaScript, just without any access to variables that the host does not want the embedded script to see.
It has less bloat if you use lots of embedded scripts. My point is that this problem has been solved before in an even cleverer way and was used by hundreds of engineers in MySpace's heyday, so I'm surprised the authors had not considered it.
