, Charles wrote

In fact, HTML5 WinRT apps are not hosted in a browser control. 

That's true, but that doesn't detract from the fact that HTML5/JS WinRT apps are parsed and managed by mshtml which is owned and managed by the Internet Explorer team.

The only difference (from a developer's perspective) is that basic objects that were there in the browser but no longer relevant are no longer there (e.g. window.status), and objects are now exposed to your javascript to interact directly with Windows.

In many ways, the whole WinRT/JS think it's just a blending of the power of WScript (with better libraries) and the swishy GUIness of HTML5, all running in a sandbox.