Replicate, although not fully free, has the bonus of outputs from Flux (from their endpoints only) able to be used for commercial purposes whereas that is normally only applicable for Flux schnell:
From the license:
"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. You may use Output for any purpose (including for commercial purposes), except as expressly prohibited herein. You may not use the Output to train, fine-tune or distill a model that is competitive with the FLUX.1 [dev] Model."
This license seems to indicate that the images from the dev model CAN be used for commercial purposes outside of using those images to train derivative models. It would be a little weird to me that they'd allow you to use FluxDev images for commercial purposes IF AND ONLY IF the model host was Replicate.
https://replicate.com/black-forest-labs/flux-dev
https://replicate.com/black-forest-labs/flux-schnell