No worries here. Ours has been in place for 4 years and it hasn't caused any problems. I lifted 1/3 of the wool rug (the part without furniture on it :-)) and pad today to check it out. It might be the same material, but our floor planks are of the factory-finished type so it was essentially chemically inert by the time it was laid. Was your floor pre-finished or finished after installation?
Our pad is only rubber on one side (the floor side), the carpet-facing side looks sort of like wool held together with a soft adhesive (very fibrous, multiple colors but mostly medium gray). I don't think I had ever really looked at it before today, the store from which we bought the rug delivered and laid it on the floor while I was at work. The rug wasn't expensive (Karastan machine-woven wool), so I'm glad that it appears that the rug store did the right thing (the floor is worth much more than the rug :-)).
