[Admin]

In user.php:
Replace

  makeyesnocode("Display email address","displayemail",1);

with

  makeyesnocode("Display email address","displayemail",1);
  makeyesnocode("Display password","displaypassword",1);

By the way, you can make it

makeyesnocode("Display password","displaypassword",0);

if you don't want it to be selected by default.

Also replace

  $users=$DB_site->query("SELECT user.userid,username,usergroupid,birthday,email,parentemail,coppauser,homepage,icq,aim,yahoo,signature,usertitle,FROM_UNIXTIME(joindate) AS joindate,FROM_UNIXTIME(lastvisit) AS lastvisit,FROM_UNIXTIME(lastpost) AS lastpost,posts,ipaddress,userfield.* FROM user,userfield WHERE $condition AND userfield.userid=user.userid ORDER BY $orderby $direction LIMIT $limitstart,$limitnumber");

with

  $users=$DB_site->query("SELECT user.userid,username,usergroupid,birthday,email,password,parentemail,coppauser,homepage,icq,aim,yahoo,signature,usertitle,FROM_UNIXTIME(joindate) AS joindate,FROM_UNIXTIME(lastvisit) AS lastvisit,FROM_UNIXTIME(lastpost) AS lastpost,posts,ipaddress,userfield.* FROM user,userfield WHERE $condition AND userfield.userid=user.userid ORDER BY $orderby $direction LIMIT $limitstart,$limitnumber");

Also replace

  if ($displayemail==1) {
    echo "<td><p><b><span class='tblhead'>Email</span></b></p></td>";
  }

with

  if ($displayemail==1) {
    echo "<td><p><b><span class='tblhead'>Email</span></b></p></td>";
  }
  if ($displaypassword==1) {
    echo "<td><p><b><span class='tblhead'>Password</span></b></p></td>";
  }

And last but not least replace

    if ($displayemail==1) {
      echo "<td><p><a href='mailto:$user[email]'>$user[email]</a>&nbsp;</p></td>";
    }

with

    if ($displayemail==1) {
      echo "<td><p><a href='mailto:$user[email]'>$user[email]</a>&nbsp;</p></td>";
    }
    if ($displaypassword==1) {
      echo "<td><p>$user[password]&nbsp;</p></td>";
    }

And there you have it.

P.S.
Why did you add the option to sort by password?
Just curious...