In my opinion it is not realistic to think that OSM would change its license to attribution-only or PD. What is realistic it that there can be other projects in the future with attribution-only or PD license and they all can live peacefully together with OSM. GeoNames http://geonames.org which is CC-BY is a good example. OSM has no trouble in showing results from GeoNames and Nominatim together http://www.openstreetmap.org/search?query=Berlin#map=12/52.5244/13.4105 On the other hand, it looks like GeoNames has no trouble with collecting data into Creative Commons Attribution 3.0 License on top of Google Maps. http://www.geonames.org/manual.html

OSM can not import GeoNames data because they are under CC-BY and OSM does not give attribution. GeoNames can’t use OSM tiles as background because that would make GeoNames ODbL. However, both parties can accept this and for the end users the situation is better than with either OSM or GeoNames alone.

Déjà vu. I suggest to read the PD threads from this archive and think if anything has changed. https://lists.openstreetmap.org/pipermail/legal-talk/2008-October/thread.html

Well, SteveC does not write here anymore which is a pity because I liked his style.

SteveC steve at asklater.com Wed Oct 22 06:50:10 BST 2008

Guys OSM isn’t going PD… can’t you go start
ReallyFreeAndOpenStreetMap.org or something?

I did not remember that Landon Blake really started to build an OSM/PD repository. We have still a wiki page about that http://wiki.openstreetmap.org/wiki/Public_Domain_Map, as well as a dedicated mailing list legal-general that was created for PD discussion.

According to this blog https://blog.openstreetmap.org/2013/10/15/the-pd-checkbox/ only 44% of active OSM accounts with at least one edit are PD friendly. It is not enough for changing the license. However, 400000 contributors could be a good start for a new crowdsourced PD mapping project.