I'm not sure if it's allowed to use. https://docs.midjourney.com/docs/terms-of-service
Can I use the images generated by Midjourney in my project?
From my understanding you can use Midjourney images commercially if you generate them while having a paid license. If you do not have a paid license when generating them, you are violating their Terms of Service. Once generated, you completely own the images and commercial rights to them, even if your subscription expires.
As per their terms of service: "If You are not a Paid Member, You don’t own the Assets You create. Instead, Midjourney grants You a license to the Assets under the Creative Commons Noncommercial 4.0 Attribution International License (the “Asset License”)." "You must purchase a “Pro” membership for every individual accessing the Services on Your behalf in order to own Assets You create."
Happy coding!
Raymond