WordPress if in term*

http://codex.wordpress.org/Function_Reference/has_term

So…

<?php 
if ( has_term('products', 'your_custom_taxonomy', $post ) ) 
{
    get_template_part('products'); 
}
elseif ( has_term( 'downloads', 'your_custom_taxonomy', $post ) )
{
    get_template_part('downloads'); 
}
?>

Change your_custom_taxonomy to whatever that taxonomy name is. I changed include to get_template_part. If this is found in a theme file, that’s the correct function to use. If it’s in a plugin, feel free to change it back.