Node with multiple parent groups

The homepage for this module says that entities can have multiple parent groups,

single-to-many: One single entity may be part of multiple Groups.

but I can't find any way to do this. I've been scouring the settings and code for the main module as well as gnode, and I can't find anything mentioning this possibility. The only thing I've found is at the beginning of gnode.module:

function gnode_entity_info_alter(&$entity_info) {
  // Nodes can only have one group parent.
  $entity_info['node']['group entity'] = 'single';
}

Is this not actually a feature? Or am I missing something?