Tier 2 Restricted open-weight
What the publisher claims: open-weights, open source, open models
The one-liner: The most-deployed open image family, whose license tightened generation by generation.
The six questions
Weights for 1.5, SDXL, and 3/3.5 are downloadable; 3.5 open weights are gated by Hugging Face agreement rather than withheld.
Commercial use is broadly permitted, but through use-restricted licenses and a $1M revenue threshold that moves large users onto an enterprise agreement.
Mature local deployment across Diffusers, ComfyUI, and many forks.
Model cards and reports describe the synthetic and curated-data mix at a high level; the corpus and recipe are not released.
Limited: the ecosystem is fully reproducible in use, not in training.
Stability's repos and the diffusers ecosystem take community PRs; direction corporate and license terms unilateral.
License
CreativeML Open RAIL-M / Open RAIL++-M for 1.5 and SDXL; Stability AI Community License for 3 and 3.5 — license source ↗
- Use-based restrictions remain in the RAIL licenses, so they are not OSI-approved open source
- Under the Community License, organizations with more than $1M in annual revenue must negotiate an enterprise license
- Terms changed across generations inside the same family
What is actually released
- weights across all generations
- inference pipelines and Diffusers support
- model cards
- technical reports and papers
Why it matters
Stability AI's own community license is the reference case for how an incumbent converts an open-weight release into a licensed-gated one without ever closing the weights.
Sources
- https://huggingface.co/stabilityai/stable-diffusion-3.5-medium
- https://en.wikipedia.org/wiki/Stable_Diffusion
- https://terms.law/ai-output-rights/stable-diffusion
Derived from the openness dataset behind But Is It Open? — snapshot 2026-11-07 ↗. Scores are qualitative readings of the cited evidence, not verdicts; tier measures openness, not intelligence.