As a member of the Pirates without Borders, you obtain voting rights within the association. For becoming a member you have to accept the statues (German).
Your only duty is to pay the annual fee of 40 € (16 € for those with limited income).
You have there ways to become a member:
By regular mail:
Print, fill out and mail the PDF by regular mail to:
Piraten Ohne Grenzen
Am Bürohochhaus 2-4
You can also use the analog method: Download the membership Application as PDF here. Fill it in legibly and send it via snail mail or scan it an send it via e-mail to firstname.lastname@example.org.