TL;DR
FLUX 3 Klein weights are under the FLUX Kommunity License v.1.0, not a “free for any business” grant. Non-commercial use is allowed. A Qualifying User may use Outputs commercially. Using Outputs to improve a similar model is prohibited. A product that runs Klein for end users needs a commercial license, according to the model page FAQ.
| Use | Under this license |
|---|---|
| Non-commercial use | Allowed. Section 2.a (i) and the definition in Section 1.c |
| Qualifying User uses Outputs commercially | Allowed, if you meet Section 1.e and the conditions in Section 2.a (ii) and Section 2.e |
| Use Outputs to improve a similar model | Not allowed. Section 4.b |
| Offer end users a product that runs Klein | The model page FAQ says this needs a commercial license |
The revenue line in Section 1.e is gross annualized revenue of you together with your affiliates, under US$5,000,000. “Affiliates” is not defined in Section 1. Prices for a separate commercial license are not published on the licensing page named in Section 2.b.
What the license actually says
The quotations below are the license text. Section numbers match the FLUX Kommunity License v.1.0 file.
Section 1.e, Qualifying User:
“Qualifying User” means you, if at any time you together with your affiliates’ gross annualized revenue is less than US$5,000,000.
Section 1.c, Non-Commercial Purpose. The opening and the “for clarity” sentence:
“Non-Commercial Purpose” means any of the following uses, but only so far as you do not receive any direct or indirect payment arising from the use of the FLUX Model, Derivatives, or Content Filters (as defined below): (i) personal use for research, experimentation, and testing for the benefit of public knowledge, personal study, private entertainment, hobby projects, or otherwise not directly or indirectly connected to any commercial activities, business operations, or employment responsibilities; (ii) use by commercial or for-profit entities for testing, evaluation, or non-commercial research and development in a non-production environment; and (iii) use by any charitable organization for charitable purposes, or for testing or evaluation. For clarity, use (a) for revenue-generating activity (including but not limited to in a production environment), (b) in direct interactions with or that has impact on end users, or (c) to train, fine tune, or distill other models for commercial use, in each case, is not a Non-Commercial Purpose.
Section 2.a is the grant. It is the clause that both allows non-commercial use and, for a Qualifying User only, commercial use of Outputs:
Subject to your compliance with this License, Company grants you a non-exclusive, worldwide, non-transferable, non-sublicensable, revocable, royalty free, and limited license to access, use, create Derivatives of, and Distribute the FLUX Model and Derivatives solely for: (i) your Non-Commercial Purposes, including non-commercial Robotics Uses; and (ii) solely if you are a Qualifying User, use Outputs, including Outputs from Derivatives, for commercial purposes, and you may access and use the FLUX Model and Derivatives in a production environment solely for the purpose of generating such Outputs, except as expressly prohibited herein.
Section 2.b sends anyone who wants a use the license does not already allow to a separate ask. The sentence is:
If you want to use a FLUX Model or a Derivative for any purpose that is not expressly authorized under this License, such as for a commercial activity, you must request a license from Company, which Company may grant to you in Company’s sole discretion and which additional use may be subject to a fee, royalty or other revenue share.
That section points to https://bfl.ai/licensing. The page names the tiers Builder, Platform, Professional, and Enterprise. It does not publish prices. This summary does not describe what each tier includes, because those descriptions are not in the license file.
Outputs, filters, and similar models
Section 1.a says, in a sentence that matters for the training ban later: “For the avoidance of doubt, Outputs are not considered Derivatives under this License.”
Section 1.d:
“Output” means any result of operating or otherwise using the FLUX Model or Derivatives, including but not limited to images, audio, video, or action-prediction outputs. For the avoidance of doubt, Output does not include any components of the FLUX Model, including any fine-tuned versions of the FLUX Model, the weights, or parameters.
Section 2.d, ownership:
We claim no ownership rights in and to the Outputs. You are solely responsible for the Outputs you generate and their subsequent uses in accordance with this License.
Section 2.e is a condition on Qualifying User use, not a suggestion. It requires either content filters or human review, and an AI disclosure when the law requires one:
You may access, use, Distribute, or create Output of the FLUX Model or Derivatives pursuant to Section 2.a as a Qualifying User if you: (i) (A) implement and maintain content filtering measures (“Content Filters”) for your use of the FLUX Model or Derivatives to prevent the creation, display, transmission, generation, or dissemination of unlawful, unsafe or infringing content, which may include Content Filters that we may make available for use with the FLUX Model (“Provided Content Filters”), or (B) ensure Output undergoes review for unlawful or infringing content before public or non-public distribution, display, transmission or dissemination; and (ii) ensure Output includes disclosures (or other indications) that the Output was generated or modified using artificial intelligence technologies to the extent required under applicable law.
Section 4 begins “You will not, and will not permit, assist or cause any third party to,” and then Section 4.b says you will not:
use the FLUX Model, any Derivatives, or any Output or results from the FLUX Model or Derivative to improve any other artificial intelligence model that performs any function similar to a FLUX Model or Derivative;
That is the clause behind “do not train a similar model on the Outputs.” It covers the model, derivatives, and outputs. It is not limited to distributing the weights.
Revocation and trademarks
Section 8.b:
We may terminate this License, in whole or in part, at any time upon notice (including electronic) to you.
Section 8.a says the license also ends automatically if you breach it.
Section 10:
You have not been granted any trademark license as part of this License and may not use any name, logo or trademark associated with Company without the prior written permission of Company, except to the extent necessary to make the reference required in the Attribution Notice as specified above or as is reasonably necessary in describing the FLUX Model and its creators.
That is why this site does not use the FLUX logo or the Black Forest Labs logo. The name is used to describe the model. The footer says the site is not affiliated with or endorsed by Black Forest Labs.
The model page FAQ, as recorded for this guide, says: “Running Klein in a product needs a commercial license.” Read that next to Section 2.a (ii), which lets a Qualifying User generate Outputs in production, and next to Section 1.c, which says use in direct interactions with end users is not a Non-Commercial Purpose. A self-serve product is the case the FAQ is talking about. It is not the same sentence as “a Qualifying User sold a picture they generated.”
Unclear areas
Two points are not settled by a definition in the file.
“Affiliates” is used in Section 1.e and is not defined in Section 1. The definitions there cover Derivative, Distribution, Non-Commercial Purpose, Output, Qualifying User, Robotics Uses, and “you.” They stop there. Whether a particular company counts as an affiliate is not answered in the license text on this page.
Attribution is required when you Distribute. Section 1.b:
“Distribution” or “Distribute” or “Distributing” means providing or making available, by any means, a copy of the FLUX Model and/or the Derivatives as the case may be.
Section 3.b then requires a prominent Attribution Notice alongside that Distribution, including the sentence that begins “This FLUX Model is licensed by Black Forest Labs Inc. under the FLUX Kommunity License.” The license does not add a separate rule, in those sections, for a hosted service that never provides a copy of the weights. That gap is left as unclear. It is not a conclusion that no notice is required.
Compared with FLUX.2 [klein]
FLUX.2 [klein], released 2026-01-15, splits licenses: the 4B checkpoint is Apache 2.0, and the 9B checkpoint is under the FLUX Non-Commercial License. It is a 4-step distillation, and the 4B line is “as little as 13GB VRAM.” FLUX 3 Klein’s image transformer is 5.6B, the distilled default is 16 steps, and the license on this page is Kommunity.