You used someone's code in an earlier post or some other thread to add to your outgoing order email, right?
That being the case, you'll have to take whatever code you added, and wrap an "if" statement around it, something like this:
Code:
if ($this->info['payment_module_code'] == 'paypal') {
// ADD CUSTOM EMAIL CONTENT HERE
}
... of course, replacing the // ADD CUSTOM EMAIL CONTENT HERE with whatever code you added
In this particular example, if the customer paid using the 'paypal' payment module, it will process your license logic. If not, it will skip it.