yeah, the only damage it does, is to your tone
Obviously, if you want to max the s**t out of the pedal and the amp, then sure something might break, but I think under reasonable conditions, theres no reason it would do any damage to any gear. As far as I know.
May sound awful though as alot of 'metal-type pedals tend to on bass IMO. (The Boss HM3 Heavy Metal is the same circuit as the Boss MT2 Metal Zone I believe, which also sucks, in my opinion of course).