It is ironic when companies like Microsoft and Google end up showing the sort of "permanent reimplentation" behaviour that used to be typical of opensource, whereas certain opensource projects persist seemingly forever. Python, Django, Emacs - these things will likely see the end of the galaxy; meanwhile, big companies now build and discard key projects every other year.
Then there's Django. Rarely changes, only for the better. Upgrading Django versions is usually painless too. The ORM is fine enough.