People share proprietary code publicly. And the fact that you're allowed to read a book doesn't (currently) give you the right to copy it and redistribute the copy.
If I read 10 or 20 books about a topic and then go teach that topic to others, do I have to attribute each thing to all the authors from where I learned it? And what if I come up with my own interpretation of a topic, do I have to trace it back to all interpretations of all the authors that influenced it? Even more, do the previous authors also have to do that and do I have to quote all the chain of references? If not, why an ML model that is supposed to learn how coding works, not memorize pieces of code verbatim, should have to “because of copyright laws”?
It does give you the right to write excerpts from memory though. If it happens to exactly match the text in the book, nobody gets excited about that, even if you could potentially rewrite the whole book.
