Add this code into the Html section in your Article Template:

<div class="tags">Tags:
{section name=$this->i loop=$this->tags}
<a href="http://www.technorati.com/tag/{$this->tags[$this->i]}" rel="tag">{$this->words[$this->i]}</a>{if $this->tags[$this->i+1]},{/if} 
{/section}
</div>

Add to your Php section:

if ($Article->keywords) {
   $this->tags = explode(",", $Article->keywords);
   for ($i=0;$i<sizeof($this->tags);$i++) {
       $this->words[$i] = trim($this->tags[$i]);
       $this->tags[$i] = str_replace(" ", "+", $this->words[$i]);
   }
} else {
   $this->words[] = trim($Category->title);
   $this->words[] = trim($Article->title);
   $this->tags[] = str_replace(" ", "+", $this->words[0]);
   $this->tags[] = str_replace(" ", "+", $this->words[1]);
}