Added language about CC-BY-SA in About

about.md

@@ -12,6 +12,8 @@ This is a very preliminary prototype. Its eventual purpose is to do for governan
 
 CommunityRule is a project of the [Media Enterprise Design Lab](https://cmci.colorado.edu/medlab/) at the University of Colorado Boulder, in collaboration with the [Metagovernance Project](http://metagov.org/).
 
+This tool is licensed under a <a rel="license" href="http://creativecommons.org/licenses/by-sa/4.0/">Creative Commons Attribution-ShareAlike 4.0 International License</a>, which means that anyone has the right to use and adapt it, the result of which must be shared under the same license. This gives communities using CommunityRule the right to learn from one another.
+
 ## Contributors
 
 Anyone who finds this project useful, or potentially so, is welcome to contribute suggestions, changes, and additions. To do so, post Issues and Merge Requests to the project [on GitLab](https://gitlab.com/medlabboulder/communityrule), or send an email to medlab@colorado.edu.