Frog lube isn't petroleum or mineral based. It's something that's organic. I don't think it's water soluble, and from what I've seen it's done a pretty good job at inhibiting rust, at least over the last 4 or 5 years, on all my mosin's. I don't have any special desiccants in my safe, which is down the basement, and the humidity is roughly 35% or so. I also know that the weapons wick FL after repeated firing and heating up. Also, there's actually a tempering process you have to go through, to remove all petroleum based lubes off your weapons before you can convert it to Frog Lube.
The only reason I converted is because my work bench is in my basement and isn't ventilated all that well. And after the "Hoppe's incident", when I thought I was having a heart attack, I made the conversion. Personally, I like the stuff, except for the cost. BUT, it's not an inhalation hazard or poisonous.