I believe Django non-rel is a fork of django, that supports non relational backends. Looking at their github it doesn't look like they have a stable 1.6 release
https://github.com/django-nonrel/django/tree/nonrel-1.6-beta
Update
There's now a stable branch for Django 1.6 available https://github.com/django-nonrel/django/tree/nonrel-1.6