Microsoft could afford to train several models for every significant class of licenses. So if you don't want the model which included e.g. GPL code in its train

Microsoft could afford to train several models for every significant class of licenses. So if you don't want the model which included e.g. GPL code in its training set, you would opt for the model that was trained on the dataset which didn't include any. It's a bit of a hassle for MS, but that would partially resolve this issue.