Misago/misago/categories/urls/__init__.py

from django.conf.urls import url

from misago.conf import settings
from misago.core.views import home_redirect

from misago.categories.views.categorieslist import categories

if settings.MISAGO_THREADS_ON_INDEX:
    URL_PATH = r'^categories/$'
else:
    URL_PATH = r'^$'

urlpatterns = [
    url(URL_PATH, categories, name='categories'),

    # fallback for after we changed index setting
    url(r'^categories/$', home_redirect),
]