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)