Great questions and thanks for reaching out.
Allowing people who haven’t purchased anything to subscribe to your Mailchimp Audience is possible when the plugin is installed and a person navigates to the page on your site that allows for account registration on your wp site. There will be an included opt-in box that says “Subscribe to our newsletter”
In regards to tracking language, Mailchimp already tries to detect Language when they join your audience, update their profile, or click links in your emails via the browser.
One way to go about allowing for a contact to choose language would be to adding an update profile link in a follow-up Automation that would invite them with a call to action to choose a language.
This could be done a few different ways such as adding a merge field that is a text field where they can type the language.
adding a pre-populated drop down list which would lend itself more consistent guarding against typos as with a simple text field.
Adding a group choice where each interest group is a language.
At this time there isn’t an option for denoting language or editing the form fields built into Woocommerce.
