Open weights vs open source: what the licences actually allow
Most models called open source in 2026 are not. Here is what Apache 2.0, MIT and community licences actually permit — and which questions to ask before you ship.
"Open source AI" is used loosely enough to be misleading. Three genuinely different things get the same label.
The three tiers
1. Open source (Apache 2.0, MIT). Use it for anything, including selling it. No field-of-use limits, no user thresholds, no attribution badge on your product. Qwen, Google Gemma 4, OpenAI gpt-oss, Mistral Large 3 and Mistral's Magistral Small are reported under Apache 2.0; DeepSeek's R1 materials were released under MIT.
2. Open weights with conditions. You can download and run the weights, but the licence attaches terms — acceptable-use rules, naming requirements, or thresholds above which you must negotiate separately. Meta's Llama family ships under the Meta Llama Community License. Perfectly usable; just not open source, and worth reading before you build a business on it.
3. Open pipeline. Weights plus training data and recipes, so the result can be reproduced and audited. Ai2's OLMo and NVIDIA's Nemotron go furthest here. This is what open source means in the sense the term was originally coined.
The questions to ask before you ship
- Can I use the outputs commercially? Usually yes, but confirm it in the licence text rather than the blog post.
- Can I fine-tune and redistribute the result? This is where community licences most often bite.
- Is there a naming requirement? Some licences require derivative models to carry the base model's name.
- Is there a user or revenue threshold? Above it, you may need a separate commercial agreement.
- Are there field-of-use restrictions? Acceptable-use policies can be updated after you have shipped.
- Has the licence actually been published? Kimi K3 was announced as an open model before its final licence text was public — a reminder that "open" is a claim until the text exists.
Why this matters more than the benchmark
A model two points behind on a leaderboard, under a licence that lets you ship without asking anyone, is worth more to a business than the leader under terms you would have to renegotiate at scale. Capability differences shrink every quarter. Licence terms do not.
For the current field and who publishes under what, see the open-weight landscape guide.
