Open-weight model licences explained

Can a business use a downloadable model?

Sometimes yes, on the terms in that model's licence. Each model has its own, and they differ a lot. This page is not legal advice. It shows what two real licences say, so you know what to look for.

What does "open weight" mean?

The weights are the numbers a model learned in training. The Open Source Initiative defines AI weights as the set of learned parameters that overlay the model architecture to produce an output from a given input.¹

"Open weight" means those numbers are published for download. It says nothing yet about what you may do with them. That's the licence's job.

Is open weight the same as open source?

No. The Open Source Initiative's definition says open source models and weights must include the data information and code used to derive those parameters.¹ Wikipedia notes that two early well-known ones, BLOOM and LLaMA, both have restrictions on the field of use.²

So don't assume "open" means "do anything". Read the terms.

What does a permissive licence look like?

Take the Apache License, Version 2.0. Its grant covers a perpetual, worldwide, non-exclusive, no-charge, royalty-free, irrevocable copyright licence, among other things.³ The full text has more conditions, so read all of it.

What does a licence with conditions look like?

Meta's Llama 3.1 Community License Agreement is one that sets conditions.⁴ It's a specific version, so newer or older Llama releases may differ. Here's what this one says:

• It grants a non-exclusive, worldwide, non-transferable and royalty-free limited licence.⁴
• If you distribute the materials, you must provide a copy of the agreement with them.⁴
• When you distribute or make available the materials, or a product or service that contains them, you must also prominently display "Built with Llama" on a related website, interface or documentation.⁴
• Use must adhere to the Acceptable Use Policy for the Llama Materials.⁴
• If the licensee's products had more than 700 million monthly active users on the version's release date, you must request a licence from Meta, which Meta may grant at its sole discretion. You have no rights under the agreement until it does.⁴

That last condition is about the licensee's scale, so read the whole agreement before deciding it doesn't apply to you.

What should I check before using a model at work?

1. Find the licence on the model's own download page, for the exact version you're using.
2. Check whether it allows commercial use, and what it asks of you if you share or build on the model.
3. Look for a separate acceptable use policy, and read it.
4. Keep a copy of the licence text you accepted, with the date.
5. If anything is unclear, ask a lawyer. Licence law differs between countries, and a maker's terms may name one place whose courts decide disputes.

Tools like Ollama and LM Studio download models for you, but they don't change a model's licence. The licence stays with the model.

A smaller quantized copy of a model often has its own download page. Check the licence shown there too.