GitLab seems to be a lot more responsive to feedback. It'd be worth asking them if they can publicly document their training set and provide a list of licenses and copyright notices.
The training data is documented in https://docs.gitlab.com/ee/user/project/repository/code_sugg...
AI Transparency is important, all available AI features provide documentation for training data, and are built with privacy first.
The GitLab Duo announcement adds more feature details and plans. https://about.gitlab.com/blog/2023/06/22/meet-gitlab-duo-the...
The AI/ML blog series provides insights on experiments, and features being built. https://about.gitlab.com/blog/2023/04/24/ai-ml-in-devsecops-...
Would it be possible to get a complete list of sources and licenses?
There's not actually anything in GPL or any other major FOSS license that prohibits using it to train an AI. The controversy stems from Microsoft refusing to follow the terms of those licenses. If they could just fulfill their obligation to propagate copyright statements and license text there would be no controversy over copilot.
Thus stating that it was trained only on "permissive" licenses doesn't actually answer the question without defining what a permissive license is.