Generate commerce file license

license_create.php

<?php

$fid = '';  // ID of the file you want to license.
$uid = '';  // ID of the user receiving the license.

$line_item_id = ''; // Optional - Id of line item in an order owned by the user.

// Get the entities.
$user = user_load($uid);
$file = file_load($fid);

$values = array(
  'uid' => $user->uid,
  'status' => 'active',
);

$license_new = commerce_file_license_create($values);

// Attach the file to the license.
$license_new->commerce_file_license_file[LANGUAGE_NONE][] = array(
  'fid' => $file->fid,
  'data' => array(
    'duration' => 0,
    'download_limit' => 0,
    'access_limit' => 0,
  ),
);

// Optional if line item exists.
$license_new->commerce_file_license_line_items[LANGUAGE_NONE][] = array(
  'line_item_id' => $line_item_id,
);

// Save.
commerce_file_license_save($license_new);