Yeah, its not clear to me how you could ever produce an ISBN database with any reasonable level of assurance that it's legit under those rules. With copyright you find multiple sources and put things in your own words. You cite your sources, and anyone can check that your sources provide the *information* which you have restated in your own words. While it's always possible that you plagiarized one source while citing another, these things can be discovered, and when two sources use the exact same words, copying is evident. With sui generis database laws, there's no way to really know if your multiple sources all are based on the same common source, and there's no way to "put things in your own words" to ensure that it doesn't matter. Moreover, the fact that one source has the exact same true factual information as another doesn't prove that one copied from another.

Aren't any of these databses copied, at least indirectly, from the database created by International ISBN Agency?

In any case, my point was that blatant violation of a TOS is more than just violation of "a private contract". It's at least potentially something much more serious. And on that, it matters quite a bit whether it's one person running an automated process or a group of people accessing the information bit by bit. The former got a brilliant young Wikimedian prosecuted. The latter hasn't.

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By the way, I just read https://meta.wikimedia.org/wiki/Wikilegal/Database_Rights and it's not clear to me exactly what the Wikimedia policy is with regard to sui generis database rights. The closest I see is "In the absence of a license, copying all or a substantial part of a protected database should be avoided." But what happens when thousands of people, working independently even, each copy an insubstantial portion of a protected database, and it adds up? I guess from a practical standpoint it'll be impossible to prove that this is what happened (unless there's a protected database which *created* the information in the first place, a la the one created by the International ISBN Agency). But then what we're really saying is not that you shouldn't violate European database law, but that you should do it in a way such that it can't be proven.

As I said above, I don't know how these laws can possibly be adhered to with any reasonable level of assurance. Maybe you or someone else on here has a suggestion?