If you have a look into generate.php you'll find that it's making use of the
searchUsers() method. Currently - without any additional parameters - this method simply returns ALL users. But if you have a look into OssnUsers.php, starting at line 625 you'll find that the search result can be in fact refined by what Arsalan named 'entities_pairs' which may be passed when calling the searchUsers method.
Thus, in case you want to generate a list of female users only for example, you would need to change the method call like
$users = $users->searchUsers(array(
'page_limit' => false,
'entities_pairs' => array(
'key_1' => array ('name' => 'gender', 'value' => 'female')
Since I've never used the categories component myself, I don't know the exact name of the entity. So just have a look into your entities database and list all entities of type 'user' and find the right subtype yourself.