[OSM-talk] License plan - what data would need deleting

[Ed Avis]

You have discussed some elaborate plans about what data from a non-relicensing
contributor would have to be deleted and what would have to be kept.

In the worst case, in the event of a dispute, do you really fancy trying to
convince a court of law that the elaborate heuristics you applied are sufficient
to make the map completely independent of the work of the users who said 'no'?

The only sound rule that can be sure to stand up in court is to delete all data
from the contributors who didn't give explicit permission, and all data that
depends on it.  Period.

You may think this is unnecessarily paranoid.  Indeed it is: but if the
relicensing exercise doesn't put the project on a legally unassailable footing,
it is not worth doing.  At the moment we can say with certainty that 100% of the
contributors have clicked 'yes' to an agreement to distribute their changes under
CC-BY-SA.  Any legal niceties tidied up by a move to a different licence are good
to have, all other things being equal, but are hugely outweighed if the data
becomes a questionable mishmash of contributions that have agreement, and those
that don't have agreement but pass some odd set of rules we invented ourselves to
convince ourselves that we didn't need to get permission.

-- 
Ed Avis <eda at waniasset.com>