I thought they just banned the use of code not embedded in your app. You are free to Jit. Just not files downloaded from the net. Only files embedded In your app

No you can't jit. For a very simple reason: you cannot allocate memory that is both writable and executable.

For those who are wondering, you can still use an embedded webview, which does end up doing just-in-time compilation of javascript.

Isn't JIT deactivated in webviews? I'm not even entirely sure it's activated in JavascriptCore.

As of iOS 8, webviews have the same JavaScript engine as Safari does, called Nitro, which I believe does do JIT compilation of JavaScript.

Well, UIWebView (the standard web view, pre iOS8) does not have Nitro, but WKWebView (introduced in iOS8) has Nitro. The only problem is that while they are similar, the WKWebview API is not feature complete with UIWebView, leading to a lack of adoption from big players such as Chromium.

[0]: https://code.google.com/p/chromium/issues/detail?id=423444

Jit is activated in webviews since iOS8

Pretty sure no JIT. Because the Mono guys had a few compat issues due to requiring ahead of time compilation for iOS. If JIT was an option then it'd certainly be used.