Hi Andrea,
I added the following code as a code snippet to your site.
Your urls should work like:
dev.YOURSITE.net/social/proposals/
dev.YOURSITE.net/social/proposals/?archive=true
function _my_gd_listing_where_filter($where){
	global $table;
	$geodir_post_type = geodir_get_current_posttype();
	if($geodir_post_type=='gd_idea' || $geodir_post_type=='gd_project'){
		$date_now = date("Y-m-d");
		$date_param = isset($_REQUEST['archive']) ? '<=' : '>';
		if (!is_admin()) {
			$where .= " AND $table.geodir_end_proposal_date $date_param '$date_now' ";
		}
	}
	return $where;
}
function _my_gd_listing_where(){
	if (!is_admin()) {
		if (geodir_is_page('listing')){
		add_filter('posts_where', '_my_gd_listing_where_filter', 10,1);
		}
	}
}
add_action('pre_get_posts', '_my_listing_loop_filter', 2);
function _my_listing_loop_filter($query){
	// fix wp_reset_query for popular post view widget
	if (!geodir_is_geodir_page()) {
		return;
	}
	if (isset($query->query_vars['is_geodir_loop']) && $query->query_vars['is_geodir_loop']) {
		_my_gd_listing_where();
	}
	return $query;
}
Thanks,
Stiofan