Method window.home() is evaluating preference browser.startup.homepage which is not set in km. Its default value (in SeaMonkey) is chrome://navigator-region/locale/region.properties (in km this is pointing to \chrome\xx-YY.jar!/embed/locale/YY/navigator-region/region.properties). In this file, string homePageDefault is set to http://www.mozilla.org/
To make window.home() have the desired effect in km, browser.startup.homepage must be set to the same value as kmeleon.general.homePage.
Possible workaround: Synchronize browser.startup.homepage and kmeleon.general.homePage with a macro.