http://oleb.net/blog/2012/10/remote-view-controllers-in-ios-6/But I doubt what will drive Apple to improve JS performance. Because making people to use Objective-C is a lot beneficial to Apple.
But I don't think it is true that this strategy is actually more beneficial to Apple. Developers want to support multiple platforms, and the least expensive way to do that is often HTML5. That's why PhoneGap is popular, despite the poor JS performance. The extra cost of doing separate apps is ultimately paid not only by third party developers, but by Apple as well. To make a long story short, encouraging a cross platform environment would allow good developers to make higher quality apps.
Much as I dislike Apple these days, the difference between iOS and Android is such that I have trouble maintaining a straight face when I hear them compared. They don't need to compete on app availability.
Not sure exactly how that would work, because permissions to allocate executable memory is given per process on iOS. But I guess they could inspect the call stack to see if the allocating call indeed comes from the built-in JSC lib?