Why does this seem to be diverged from https://wordpress.org/plugins/mailchimp/? Here, the latest version is 1.4.3 and the one installable from the the website is 1.5.1. I noticed because of the very old translation files in the one installable from wordpress.com. Looking at the readme it seemes to have diverged after 1.4.2.
See https://wordpress.org/support/topic/translations-outdated