If you want true legal permission to make and distribute paper model diagrams you need to get written consent from Gearbox. You can’t do it here and protect yourself if for some reason you are concerned about being criminally charged by Gearbox.
Go to the Gearbox home page and select “Business Development or Licensing” and type a short description of your concern and wish to receive written consent to make paper models. They should respond back regarding any permissions they would require, or direct your inquiry to the appropriate channels.
Personally I have never heard of anyone being held liable for infringement if they are not charging, or if they are not making claims of ownership. People have been sharing paper models for decades and I could not find a single case in the US court system that is related to the subject matter, however I only did a few standard searches.
Just make sure that you need an actual document to get permission if that’s what you want. A forum post from a company rep wouldn’t hold up in court as far as I know.
Maybe someone else around here would know more?