don't they fall awfully close to flamethrowers, in that they burn stuff, and as such not that 'human'
I tend to regard any conception of being humane with your weapons as a joke. They banned shotguns before WW2 believing they'd cause gross injuries, but they didn't ban mortars, hand grenades, artillery... Hell even the high-velocity rifle bullet as used in that war pretty much made a mockery of the shotgun ban. If you wanted to be humane, you wouldn't be using weapons.
The point is that in the end the only real distinction between weapons is whether they were designed to be lethal or not, and that distinction only even came into existence within the last twenty years. When you're dead, you're dead. You don't much care how you died, because the dead have little use for pity or vanity.
So the world has few man-portable options for killing things with fire? 
FLASH and its cousins are quite up to the task, in the end, depositing about a pound of similar-to-napalm-but-ignites-on-contact-with-the-air burning material on you at ranges of up to 200 meters. I was simply surprised at how few alternatives there were, given the demonstrable effectiveness of fire as a weapon.
Molotovs
Possible, I suppose, but incredibly inconvenient to carry and use against other human-sized targets. (Yes, I'm researching ways to set people on fire from a distance. It makes sense in the context of what I'm writing; if you have someone who can stand up to getting hit in the chest with a LAW rocket about 60% of the time, but can still have their lungs seared, you work on ways to set them on fire.)
