The sale in the download's section is now over.

the demo links on the download pages for some but not all don't work they redirect to

kasl.info/n/a    where i assume demo link was n/a 

you should add an if() statement eg 

<?php  
if($demo_link != "n/a"){  
 echo "<a href=\"http://demo_link.com/file.txt\">Demo</a>"; 
} 
?>

on another note... no wait same one, how about adding a if() statement for if file purchased they don't see the purchase link

no n/a just ment there is no demo. fixed now