Goodreads allows you to export your library via CSV.

Right, if the question is asking about exporting your book lists from Goodreads and then (eventually) importing them into Booqsi, that's definitely allowed.

Yes, sorry! I may have phrased that incorrectly - I meant exporting your Goodreads data and importing them into Booqsi (which Storygraph allows you to do, though it can take some time).

GDPR demands a machine readable export of your data. You could import that and I can't see how this could violate any ToS.

Well I don't think importing tweets and displaying them is allowed by their ToS for instance (even though some apps do), nor instagram pics.

The user owns the data, not the platform. The data is just ISBN numbers, dates, review comments and so on anyway.

It would probably be illegal to crawl Goodreads, if that’s what you’re thinking about?

I believe in some cases (e.g. instagram) the user agreement you sign when using the site makes your copyright over e.g. the pictures you upload be handed over to the site owners (again, to prevent competition). Just to point out that the common sense idea that "you own the data" thing isn't always true. Nevertheless this question has been resolved through other comments on here so it seems not to be the case in this scenario.

Just noting that GDPR is an EU law, not an international one.