Which licenses would it be ok that the training material is licensed under, though? If it produces verbatim enough copies of eg. MIT licensed material, then att

Which licenses would it be ok that the training material is licensed under, though? If it produces verbatim enough copies of eg. MIT licensed material, then attribution is required. Similar with many other open source-friendly licenses. On the other hand, if only permissive licenses that also don't require attribution is used, well, then for a start, the available corpus is much smaller.