Hey Paul,
If you look at the top of the FastSpring PHP script you'll see the following:
$post_data = array( 'method' => 'limelm.pkey.generate', 'version_id' => $version_id, 'num_keys' => 1, 'num_acts' => $quantity, 'email' => $email, 'api_key' => $api_key, 'nojsoncallback' => 1, 'format' => 'json');
So if you want to generate 2 activations for every order, you can change the "num_acts" line to the following:
'num_acts' => $quantity * 2,
Does that make sense?