Apparently the XML API is no more. https://isbndb.com/apidocs describes their current API.
Yes, there is a new API, but it costs money to access the database. Unless someone is paying for the access, I won't develop/update the ISBNdb search. Even if so, either the API key must be shipped with KBibTeX for anyone to use or every interested user must acquire his/her own API key and pay for it.
Could you simply remove it then?
(In reply to Volker Fröhlich from comment #2) > Could you simply remove it then? It has been removed as of commit a0971a1bb3bdd0405745609ea88b282a45109cc7 The essential change is the removal of the addEngine(..) invocation for OnlineSearchIsbnDB. As I do no longer maintain version 0.4.1, you would have to edit the source code yourself and recompile/package KBibTeX. Please contact the Debian folks on how to do that for Debian. Still, I would recommend to upgrade to a newer version of KBibTeX. Even if you are still using KDE4, the 0.7.x series was the last to be release for this KDE version. I may be open to fix bugs there.
Hm? I didn't say 0.4 anywhere.
Anyway, I can see that you already disabled it in May. Thanks!