My Facebook Canvas app has a closed Facebook group associated with it. I would like to auto add users who install the app to this closed group. The Facebook UI doesn't allow adding non friends to a group, is it possible via the API ? Also there doesn't seem to be any app permission associated with it.
There probably won't ever be a way to automatically add a user to a group. Currently the Facebook group api only allows you to view membership details. Facebook may eventually allow you to invite users to the group using their group api. On that documentation link in the comments, a Facebook employee named Tiffany Chang Black comments that adding/removing users is not currently supported.