All existing users are encouraged to upgrade to version 1.6, which is the first stable release. This version includes much better support for Memberships, as well as nice-to-have features like pre-filling GoCardless forms from Profile data for address, email, phone.
This extension is working well for collecting regular donations from UK supporters.
Using it you can enable supporters to set up direct debits and every month when GoCardless takes payment this extension adds to and updates your CiviCRM contributions automatically. If someone cancels their Direct Debit this also updates your CiviCRM records. This extension uses the latest GoCardless API.
Please see the README file for full details, development status and how to install. It has been used in production since November 2016 and is actively supported.
Nb. There is another GoCardless extension available by Veda which allows using GoCardless to set up mandates but nothing else. This extension was built later, uses the newer GoCardless API, has more features (as outlined above), and is actively maintained. Please see Github repo for issues etc.