Attempt to properly describe OA licenses

public/attribution.md

@@ -2,6 +2,6 @@
 * Geocoding by [Pelias](https://pelias.io).
 * Data from
    * [OpenStreetMap](http://www.openstreetmap.org/copyright) © OpenStreetMap contributors under [ODbL](http://opendatacommons.org/licenses/odbl/)
-   * [OpenAddresses](http://openaddresses.io) under a [Creative Commons Zero](https://github.com/openaddresses/openaddresses/blob/master/sources/LICENSE) public domain designation
+   * [OpenAddresses](http://openaddresses.io) under [various public-domain and share-alike licenses](http://results.openaddresses.io/)
    * [GeoNames](http://www.geonames.org/) under [CC-BY-4.0](https://creativecommons.org/licenses/by/4.0/)
    * [WhosOnFirst](https://www.whosonfirst.org/) under [various CC-BY or CC-0 equivalent licenses](https://whosonfirst.org/docs/licenses/)