I think I am getting closer to getting an answer to the legal question.
In the mean time here is the precautions taken by someone who has done this process.
During the entire casting operation, as a safety precaution, I would wear protective clothes. These included long leather welder's gloves, leather welder's arm protection and apron, and complete face protection, consisting of an arc welder's head and face shield. (of course, I only used the clear glass in the viewing port, not the darkened glass!). Other sensible precautions were also taken, such as having a fire extinguisher available (although it may not extinguish burning propellant) and keeping anything at all flammable away from the casting operation. I always had a large pail of water nearby (water can extinguish burning propellant by means of heat absorption).