Is there a Django application similar to Drupal's Organic Groups module?

Basically I am looking for the following:

• Groups can be created by users of the site.
• Users can apply to join a group.
• Every group has a group administrator which can approve or reject applications to join a group. Also, they can remove members from a group.
• Content can be created which is associated with the group. Only group members can create content. Users who are not group members can view this content but not create/modify the content.

Are there any Django applications which can help implement these requirements?

The only one that I'm aware of is part of the Pinax project. It doesn't meet all of these out of the box, but can be expanded pretty easily to get these features.