If Github's interpretation of copyright law holds, we can train a model on proprietary code and extract concepts without having to worry about being tainted.
Is that really true? Proprietary source code is usually not available, at least not legally (and I doubt that it would be legal to train a model using illegally obtained code). And if it is available, is using it to train a model allowed? For free software, this seems obvious, because of freedom 1 and maybe 0. But do proprietary licenses allow using code in such a way? Or is this something they can't restrict because of limitations/exceptions to copyright?