BuddyPress.org

Try:

function example_insert_category( $group_id ) {

  $group = groups_get_group( array( 'group_id' => $group_id ) );
  $name = $group->name; 
  $slug = $group->slug; 

  wp_insert_term(
    $name,
    'category',
    array(
      'description' => 'This is an example category.',
      'slug'    => $slug
    )
  );
}
add_action('groups_group_create_complete', 'example_insert_category', 1, 1);