Zindus is using HTTPS/SSL to connect to Google and stores POP3/IMAP passwords using the same mechanism that Thunderbird uses to store your POP3/IMAP passwords. The mechanism allows you to use a master password to encrypt stored passwords. See http://www.zindus.com/faq-thunderbird/#toc-security for details.
Simply use the default installation method. See https://addons.mozilla.org/de/thunderbird/addon/6095 to get the