Humanitarian aid has always been a weapon, of sorts. Indeed, historically more soldiers died from sickness or disease (humanitarian problems) than from fighting (military problems). I imagine that in less developed areas of the world the same is still true. You cannot give aid to one side, regardless of the type without hurting the relative advantage that the other side holds.

I hate to sound relativistic, but the idea of Just War, to me is just something to let others sleep well. After all it wasn't until the 20th Century with moralists like Reinhold Niebuhr that anyone even thought about the idea of there being such a thing as moral war, as a function of its structure or motivation. Either you believed that war was a contest between good and evil, and therefore one side was evil (i.e. not yours), or you thought that war was inherently evil, and therefore there was no such thing as just war.

To me, people who try to justify war by looking at its structure are missing the forest for the trees. Humanitarian or not, who you help is the important issue, not the structure of the conflict.