Just looking at the eval datasets used in the HF leaderboard, ARC is CC BY-SA, TruthfulQA is Apache, and HellaSwag and MMLU are both MIT. The first dataset many people will explore ml with, MNIST, is GPL-3.0 license. The audio courpus datasets I've used have all been similarly permissively licensed, for example LibriTTS is CC BY 4.0. LJ Speech, one of the main datasets used in Tacotron is public domain. Maybe I should have been more explicit and used the term permissively copyrighted instead to help avoid confusion.

https://huggingface.co/spaces/HuggingFaceH4/open_llm_leaderb...