Open Database License

The Open Database License (ODbL) is a copyleft license agreement intended to allow users to freely share, modify, and use a database while maintaining this same freedom for others.
ODbL is published by Open Data Commons, which is part of Open Knowledge Foundation.
The ODbL was created with the goal of allowing users to share their data freely without worrying about problems relating to copyright or ownership. It allows users to freely use the data in the database, including in other databases; edit existing data in the database; and add new data to the database. The license establishes the rights of users of the database, as well as the correct procedure for attributing credit where credit is due for the data, and how to make changes or improvements in the data, thus simplifying the sharing and comparison of data.
Notable uses.
The OpenStreetMap (OSM) project completed the move from a Creative Commons license to ODbL in September 2012 in an attempt to have more legal security and a more specific license for databases rather than creative works.
Other projects using ODbL include OpenCorporates, Open Food Facts, and Paris OpenData.