Instead of updating the phplb deep links mod, I prefer to post this here to leave both options available. Either deeplinks should be required, this was done in the previous mod or optional, instructions below.

Step 1: Apply the mod in phpLinkBid Deep links MOD

Step 2:
1. in file buy.php
FIND:

$kForm->addRule('link_deep_title1', 'title');
$kForm->addRule('link_deep_title2', 'title');
$kForm->addRule('link_deep_title3', 'title');
$kForm->addRule('link_deep_url1', 'url');
$kForm->addRule('link_deep_url2', 'url');
$kForm->addRule('link_deep_url3', 'url');

REPLACE BY

$kForm->addRule('link_deep_title1', 'deep-title');
$kForm->addRule('link_deep_title2', 'deep-title');
$kForm->addRule('link_deep_title3', 'deep-title');
$kForm->addRule('link_deep_url1', 'deep-url');
$kForm->addRule('link_deep_url2', 'deep-url');
$kForm->addRule('link_deep_url3', 'deep-url');

2. in /klib/class.kForm.php
FIND

case 'url':
if(!$validate->is_url($data[$name]))
$this->controls[$name]['errors'][] = 'Invalid URL';
break;

AFTER IT ADD

case 'deep-url':
if(!$validate->is_url($data[$name]) && ($data[$name] != 'http://'))				
$this->controls[$name]['errors'][] = 'Invalid URL';
break;	

case 'deep-title':
if(!$validate->is_title($data[$name]) && ($data[$name]))	
$this->controls[$name]['errors'][] = 'Invalid title';
break;