Open-Weight Isn't Open Source: Why the Label Is Broken
Open-weight and open source AI are not the same thing, and the gap between downloadable weights and fully disclosed training data, code, and evals defines a real spectrum rather than a marketing checkbox. Nearly every model marketed as open source today — Llama, DeepSeek, Qwen, Mistral — is open-weight only, while true full openness stays confined to smaller research models. Regulators, especially under the EU AI Act, are now writing their own definition of "open" tied to concrete exemption criteria, which will matter more than any lab's self-description. For PMs, the license terms attached to an "open" model can cap your user base, restrict redistribution, or evaporate your compliance exemption without warning.
