Sdp:Open and free

From SensorDataLab

Open and free data can be gathered at no cost (for the end user) and be used and redistributed without explicit consent from the author.

This may be because the author has given permission beforehand (using a Creative Commons license, or Open Data Commons license), or because the data is or has been put in the public domain (such as data provided by the US government).

See Wikipedia:Creative Commons licenses, Open Data Commons, Wikipedia:Public Domain.