Providing a patch

http://dev.ckeditor.com/wiki/Contribute

//Ability to support both vbox and hbox layout
if ( elementDefinition.labelLayout != 'horizontal' )
    new CKEDITOR.ui.dialog.vbox( dialog, [], inputHtmlList, html );
else

        new CKEDITOR.ui.dialog.uiElement( dialog, labelDefinition, inputHtml, 'label', null, { id : labelId, 'for' : inputAttributes.id },
        item[0] );
        inputHtmlList.push( inputHtml.join( '' ) );
    }

    //Ability to support both vbox and hbox layout
    if ( elementDefinition.labelLayout != 'horizontal' )
        new CKEDITOR.ui.dialog.vbox( dialog, [], inputHtmlList, html );
    else
        new CKEDITOR.ui.dialog.hbox( dialog, [], inputHtmlList, html );

    return html.join( '' );
};