firegesture-logically-open-link-or-duplicate-tab-next-to-current.js

// if the gesture started from a link, open link in new tab
var linkURL = FireGestures.getLinkURL(FireGestures.sourceNode);
if (linkURL) {
    gTabDeque.moveTabToSecondPlaceInDeque(gBrowser.loadOneTab(linkURL, {inBackground: true}));
    return;
}

// else duplicate tab
gTabDeque.moveTabToSecondPlaceInDeque(gBrowser.loadOneTab(gBrowser.currentURI.spec, {inBackground: true}));