Legal concerns

Dezoomify is a free and open source software distributed under the GPL license. You can use it, modify it, and redistribute it freely under the terms of this license.

The authors of the software decline any responsibility for the usage you make of it. In particular, please keep in mind that it's not because a free software gives you the technical ability to download a picture that you gain the right to use it however you want. Intellectual property and copyright laws still apply : being able to download a picture is not an excuse for not respecting its copyright. In particular, redistributing copyrighted works you don't own may expose you to sanctions.

The authors, maintainers, and hosts of dezoomify are not responsible for the use you make of the tool.

International copyright is hard. To determine the effective copyright of any work when the countries of the author, location of production/publication of the work, hosting by 3rd parties and the country of the downloader need to be taken into account, is complex and you should consult an IP lawyer if you want certainty about the legality of your (intended) usage.