If I have catcoins at exchange, are they "safe" there in term of this fork ? (i know exchange owner can run away with them, but that's not what i'm asking here:) )
You can withdraw them on whatever chain the exchange is on. If they update to the forked version, you'll be fine.
If you want to be on the safe side, withdraw them before the fork happens. That way you can spend your coins on both chains, no matter which one survives.