There has been a number of people in Australia reporting that they have been stopped and questioned and/or had a gun pointed at them due to their activities associated with OSM. Same thing happens to Geocachers and a solution they came up with was to produce license like documents to help explain their presence.

http://img189.imageshack.us/img189/1008/geocachinglicencetempla.png

So I went ahead and mocked this one up:

http://map-data.bigtincan.com/data/osm-license.png