Membership Module for Drupal 8
I've recently published a development branch of the Membership Module for Drupal 8. Thanks to László Csécsy (Boobaa on Drupal.org) for opening up the membership namespace to a Drupal 8 project, and for his previous work on the D5 module.
Similar to the general idea behind Membership Entity module for Drupal 7, I'm envisioning a rather unopinionated framework. At the moment there is support for states and workflows courtesy of State Machine, plus an optional "Membership Provider" submodule that exposes a plugin type to integrate with APIs or other modules that would manipulate memberships. There's not much in the interface for this plugin (yet) so I'm interested in others' ideas for a framework there.
I've really enjoyed working in Drupal 8 and this module has allowed me to dig deep into the plugin and entity APIs. Drupal Console has been a huge help in scaffolding otherwise-tedious elements, like content entities with a UI.