We've moved the code and SDK to JavaCommerce. You can now see it at http://sourceforge.net/projects/javacommerce.
This time JDK 1.3 and JDK 1.4 support are included.
PayPal Tools is a collection of utilities which are used to process website payments via PayPal. Included is a Cryptography Utility which can be used to create Encrypted Website Payments, a TagLib which can be used to create JSP-based PayPal Buttons (both encrypted and unencrypted), and a Utility class which contains various API helper methods.
It's still just for JDK 1.3 right now, but the documentation is there. Look for JDK 1.4 soon.
It's for JDK 1.3 right now, and documentation is fairly sparse, but it works. Send me an email if you have any questions/problems.