Comment by yuvadam
I don't think it's possible to separate any open source contribution from the ones that came before it, as we're all standing on the shoulders of giants. Every developer learns from their predecessors and adapts patterns and code from existing projects.
Exactly that. And all the books about, for instance, operating systems, totally based on the work of others: their ideas where collected and documented, the exact algorithms, and so forth. All the human culture worked this way. Moreover there is a strong pattern of the most prolific / known open source developers being NOT against the fact that their code was used for training: they can't talk for everybody but it is a signal that for many this use is within the scope of making source code available.