Hi,
since BF 1.5.9 build 696 people can add PayPal to their forms including paid downloads.
In order to use PayPal as merchant you need the so called tokens.
Here is a little howto for obtaining it, thanks goes to Elliot!
#### PayPal token howto
You have to enable Payment Data Transfer, and to do so follow these steps:
Go to the PayPal website and log in to your account.
Click "Profile" at the top of the page.
Click the "Website Payment Preferences" link in the Selling Preferences column.
Click the Payment Data Transfer "On" radio button.
Click "Save."
It might say in order to use Payment Data Transfer, you must turn on Auto Return. If so turn that on.
A confirmation message will appear at the top of the page indicating that you have successfully enabled Payment Data Transfer.
Your identity token will appear within that message, as well as below the PDT On/Off radio buttons.
As part of the Payment Data Transfer process you will need to pass PayPal the identity token, along with the transaction token, in order to display the transaction details to your customers. For more information on Payment Data Transfer, please refer to the Order Management Integration Guide by following these steps:
Go to the PayPal website and log in to your account.
Click the "Merchant Services" tab.
Click "View all Features" under the PayPal Website Payments Standard section.
Click '"Backend Integration."
Click "Learn more" in the Payment Data Transfer section.
Click "Manual."
Click "Order Management Integration Guide."
To view this guide, Adobe Acrobat Reader software is required. We recommend using the latest version available for your operating system. To download or update Adobe Acrobat Reader, click 'Adobe Acrobat'.
Once Payment Data Transfer has been turned on, Payment Data Transfer notification will occur when a user has completed their payment. If PayPal Account Optional is turned on then a new user will need to choose to continue to your website in order to trigger Payment Data Transfer notification.
If you also need notification of transaction reversals (such as chargebacks), refunds, and subscription events, please also enable Instant Payment Notification (IPN)