Reciprocal Open License

= "anyone can use my data, but whatever they use it with must also be exposed under this license" [1]

Example: the Open Data Commons license developed by Talis

Comment: "the copyleft nature of the license probably wouldn't appeal to many social networking services who see their data garden as business value." (http://blogs.talis.com/nodalities/2008/01/data_licenses_for_social_netwo.php)

More Information

1. Data Portability Licenses
2. Open License