What can you legally do with a model you downloaded?

Having the weights on your disk does not tell you what you are allowed to do with them. The license does. Before you build anything, read it, because the answers vary from “almost anything” to “ask permission first.”

A few questions are worth asking of every license. Can you use it commercially? Under MIT you can, including inside paid closed-source products.^[1] Can you fine-tune it? Permissive licenses let you modify freely; restricted ones may attach conditions, such as Llama’s rule that a model trained from it carries “Llama” in its name.^[2] Is there a usage cap? Llama’s license requires very large products, above 700 million monthly active users, to get separate permission from Meta.^[2] What about attribution? MIT asks only that you keep the notice;^[1] Llama asks you to display “Built with Llama.”^[2]

One thing weights alone cannot give you is the right to retrain from scratch or fully audit the model, because the training data and code are usually not included.^[3] So “I have the weights” is not the same as “I can reproduce or deeply inspect this model.”