If you are using Subscriptions to manage all of the billing and you plan on using another system for some other part of your subscriptions, you will need to know who is an active subscriber. There are some plugins out there that do just this.
You must have the WooCommerce Subscriptions plugin installed and activated on your site. You should also have a subscription product already created.
You will also need to purchase and install the WooCommerce Subscription Exporter plugin from http://codecanyon.net/item/woocommerce-subscription-exporter/6569668.
To export subscription orders, perform the following steps:
The default options for this plugin are quite useful and most likely don't need to be changed. However, if you need special formatting for your CSV file, you can manipulate all sorts of settings by going to WooCommerce | Subscriptions Export | Options.
You can do a lot with the WooCommerce Subscription Exporter extension—more than just exporting active subscribers. You could also run a report that lists all users who cancelled their subscription in the past three months. You could get all of their e-mails and ask them why they left. Exporting active subscribers is really just the beginning.