There's no wheel being reinvented. XULRunner is based on XUL, which makes it fundamentally different from the goal of above projects (that is, to use HTML technologies alone to build 'native' apps).
Some of us at Mozilla Labs have tried to fill this gap through the Chromeless project (https://github.com/mozilla/chromeless), but we've stopped working on it in favor of a more general runtime for web apps (that's what I was talking about in the last sentence: https://wiki.mozilla.org/Apps/WebRT).
The very fact that XULRunner/Chromeless didn't take off like PhoneGap did in the mobile arena for example is evidence that there's room for innovation in this space.
Happy to elaborate on this, but only if you promise you'll be nicer :)
I´m sorry if my comment could be read hostile, it was not intentional.
But what I don´t understand is what more are you trying to achieve that cannot be done in XUL with a browser tag (https://developer.mozilla.org/en/XUL/browser), and where you can stick to vanilla html/js/css, if XUL is not an option?
Some of us at Mozilla Labs have tried to fill this gap through the Chromeless project (https://github.com/mozilla/chromeless), but we've stopped working on it in favor of a more general runtime for web apps (that's what I was talking about in the last sentence: https://wiki.mozilla.org/Apps/WebRT).
The very fact that XULRunner/Chromeless didn't take off like PhoneGap did in the mobile arena for example is evidence that there's room for innovation in this space.
Happy to elaborate on this, but only if you promise you'll be nicer :)