Richard
(Richard Fairhurst)
3
PDDL effectively means “we claim no rights in this data”. Therefore there’s nothing to “enforce” - anyone can do anything with it.
That means it’s a great choice for incorporating into OSM under the current or proposed licence, or indeed into any database anywhere.
However, if a user extracts the data from OSM, it will then be subject to OSM’s (more restrictive) terms.