ABC could tell the person who put it up on Youtube to take it down, and would be able to take legal action against him if he refuses. I was watching a programme (can't remember what) and some comedian was on there saying that a user on Youtube had put up his live tour for viewing. So he contacted them asking them nicely if they could remove it, as he was still touring with the material and they were going to bring out a live DVD with it on, the user happily removed the link.
So I guess if ABC knew about this they wouldn't be too happy as its in direct competition with their DVD plus they own the copyright.
BTW heres a link to his DVD, its described as being classic episodes, maybe Series 1?
Heres another one, pretty sure this is Series 3.
http://shop.abc.net.au/browse/product.asp?productid=726476