I am using the attached code myself to copy over tags produced with django-tagging to django-taggit.
On a dev-server I'm running both tagging and taggit in parallell as I figure out all the migration-issues, and I use the command to resync the taggit-tags.
manage.py command for migrating from tagging to taggit
-1, the thing is a year old and if someone needs it he can just c&p it for a onetimer into his source.
closed as per the ticket.