I had a hard time deciding where to post this. Even though it appears as though no NFA laws will be involved, I thought that this was the most appropriate place.
It seems as though a company called Ion Productions is getting ready to release a civilian legal flamethrower. The Washington Post reports that it is legal in all states except Maryland and California (of course) and that it rquires no background check.
http://kitup.military.com/2015/03/video-doesnt-personal-flamethrower.html#more-29592