We worked on migrating AIESEC.net which was running on (open)acs 3.x to dotlrn 1.0 /openacs 4.6.3. It was a migration of a huge system. The scripts were based on MIT sloan's scripts. A lot of changes and additions had to be done .. many AIESEC specific. IMHO it might actually make more sense to migrate directly to openacs 5.x , even the migration process would be easier as the system has better APIs.