ArrizX, The composition made by the armed forces has the viscosity of rubber. However, There are many different kinds that are in fact napalm. Napalm is a chemical composition that is made to burn anywhere from a few seconds to many many hours, sometimes days.
Although they are not one in the same, other make ups have the same basic principal but are merely not as potent as the militarys variation.
For instance, I have a recipe that uses alot of toothpaste, lighter fluid, and something else (I would have to find my paper) and it burns for only about 10 minutes, But it still qualifies as napalm