According to the legend, they weren't allowed to publish PGP on the internet because US laws forbade exporting of cryptographic tools, so they made a book with the entire source code and shipped that overseas.
Yes, export regulations were heavy back then. To have proper SSL in your Netscape, you had to import this patch file from Australia. And then we had this whole Crypto Wars thing going on. Look at Steven Levy's excellent book on the subject, or search on the Wired archives.