Real Copaslip has a a paraffinic base, which is relatively inert and doesn't seem to have a detrimental effect on most rubbers. It isn't recommended for use on brakes however, and is no use where you want lubrication - it isn't intended for that. Silicone greases are the best stuff to use.
It does, however, dry out quickly and stick the pads to the piston and caliper. That's the only place I use it on brakes, and have done for 30 years without any problems.