And then you go to the Features page, with a box on the right clearly listing "GNU/Linux and Unix / Windows / Mac OS X" as supported plartforms :) With "Native look and feel" in the box just below.
I disagree with the current GTK direction, but it's not my project and I accept that. If the focus of the project has changed, update the website(s) and documentation.
Benjamin Otte recently added uxtheme.dll support to the CSS engine and I've already seen a few screenshots of the win32 theme using it to okay effect. I wrote a patch to add OS X cursor support to GDK last year and it was taken, not to mention work by Christian Hergert and others to improve the relatively new GDK/Quartz backend. So I'm pretty sure Windows and OS X are supported platforms :)
I disagree with the current GTK direction, but it's not my project and I accept that. If the focus of the project has changed, update the website(s) and documentation.
Also the HTTPS stuff pointed out by distances.