Maxime Lathuilière, 08/09/2014 16:41:
Google Books API's Terms of Service https://developers.google.com/books/terms is elusive regarding the licence but it certainly isn't CC0. Meanwhile, I guess I'm allowed to copy the information by hand, right? It's just facts about the item, I'm using this API just like I would have used a newspaper or anything as a reference, right? But could I automate or semi-automate (à la wikidata game) the import process without being in infringement with either Google or Wikidata policies? I would just do the exact same thing - taking facts somewhere in the world and adding them to wikidata - but more efficiently, no?
Most of that is probably non-copyrightable and Wikidata is hosted in USA which have no database rights, so it can be legally ok, at least in some fashion. It's however hard to draw a line, so if there are alternatives it's better to use other data sources. See also the rather unconclusive https://meta.wikimedia.org/wiki/Wikilegal/Database_Rights
Moreover, the Google ToS are very clear in forbidding any activity which would result in you having a copy of their database/of the data the API provides access to, IIRC even in form of a cache. However, you only want ISBN? *If* you care about respecting your contract with Google, it may be wise to directly ask them if they're ok with it.
Nemo