Heath Ledger as the joker, did he have any script?

[courtkid1012]

I was reading this thing because I wanted to see if he really locked himself in a hotel for a month (which said it is true) and I saw that the director gave him free reign to say whatever he wanted. Does that mean that whoever directed The Dark Knight really said to Heath Ledger something like "You can say whatever you want, it just has to be along the lines of...."?