If the password hashes aren’t salted they can be cracked with a rainbow table - every password up to (whatever length the rainbow tables go up to now - 10 chars?) is easily cracked in seconds

I expect Internet archive salts their password hashes.

It doesn’t matter if the salting method is known, all salting methods are known and it’s easy to see what salt a password is hashed with as you need to know so you can hash a received password the same way for validation