Copyright violation?

OpenStreetMap has a changeset discussion facility where you could take an individual changeset that this user has produced, and explain why you think it may be a copyright problem. You did that in a note which is also good, but a changeset discussion entry would be directly linked to the data in question. Also, don't write "possible copyright infringement" but put it as a question: "Dear BGRDave, are you sure that the material you are taking this data from is not copyrighted? Also you seem to have modified a surveyed way here ... have you actually been to the place or are you assuming that the park map is better than manually surveyed information?" -- This will also lead to the mapper being notified about a comment on one of his changesets. Then when he doesn't reply, or tells you to leave him alone, the Data Working Group can take things further.