Taking artists’ work without consent or compensation goes against the spirit of open source, though, doesn’t it?
It doesn't. Making observations about others' works is a well-established tool for any researchers, reviewers, and people inventing new works. A concept which work perfectly within the open source framework. That's all these models are, original analysis of its training set in comparison with one another. Because it's a step one must necessarily take when doing anything, doing this doesn't require anyone's permission and is itself a right we all have.