if you wanted to hack a runescape acount the only real way of doing it would be to keylog the person. YOu could try running a brute forcer but if you try to log on to rs with the wrong pass to many times you have to wait 1 minute before you can try it again, meaning that the brute would take absoloutly years to work.
Also zezima (the number 1 dude)'s account get locked down if his password is typed in incorrectly too many times.
Sorry dude, they aint stupid.