BuddyPress.org

Try, after while ( bp_groups() ) : bp_the_group(); :

$args = array( 
    'group_id' => bp_get_group_id(),
    'exclude_admins_mods' => false
);

$group_members_result = groups_get_group_members( $args );
$group_members = array();

foreach(  $group_members_result['members'] as $member ) {
	$group_members[] = $member->ID;
}
 
echo implode(", ", $group_members);