DjangoBB использует систему аутентификации django, как вы можете видеть из ее кода:
views.py
def reply(request, thread):
"""
If a thread isn't closed, and the user is logged in, post a reply
to a thread. Note we don't have "nested" replies at this stage.
"""
if not request.user.is_authenticated():
return HttpResponseRedirect('%s?next=%s' % (LOGIN_URL, request.path))