Protocol III states that it prohibits, in all circumstances, making the civilian population as such, individual civilians or civilian objects, the object of attack by any weapon or munition which is primarily designed to set fire to objects or to cause burn injury to persons through the action of flame, heat or a combination thereof, produced by a chemical reaction of a substance delivered on the target. Under most circumstances, that is not the primary purpose of any WP munition, although it could certainly be misused.

The "definitions" section of Protocol III includes, among other things, the following: Incendiary weapon" means any weapon or munition which is primarily designed to set fire to objects or to cause burn injury to persons through the action of flame, heat, or combination thereof, produced by a chemical reaction of a substance delivered on the target. (a) Incendiary weapons can take the form of, for example, flame throwers, fougasses, shells, rockets, grenades, mines, bombs and other containers of incendiary substances.
(b) Incendiary weapons do not include:
(i) Munitions which may have incidental incendiary effects, such as illuminants, tracers, smoke or signalling systems;

None of this means that this is a "good" weapon, if there is such a thing, or that it won't cause horrendous injuries to anyone who comes into contact with it.