That is a very good point.
We considered whether data existing before a licence change would be covered, but we hadn't factored the potential need for gaining permissions for a change to be considered effective.
We have proposed that miners be the main beneficiaries of licensing and there is a consideration on whether they should vote to adopt the new terms. While not the preferred route, that would overcome any issues to what is an otherwise honest 'error and omission.' There doesn't seem to be anyone who could claim to have suffered any economic losses so this may not be an issue. It merits further investigation.
The block chain is in perpetual change, so the sooner a change is agreed upon, if at all, the more data it will cover without any reservations. At any rate, we believe the changes would be considered effective on a retrospective basis.