Expression of congratulations or approval. The precise U.S. equivalent is Good for, as in Good for you!, Good for him!, Good for us!, etc. It’s an Australianism and (in the manner to No worries and kerfuffle) appears to have been taken up first by the Brits and then by the Yanks. The ur-form is Good on ya, mate!
Another scene, the Elton John party, held in Taj Mahal-size tents outside Pacific Design Center off Melrose. Ever the pessimists, we gird ourselves for letdown. It’s the 16th year Sir Elton has done this, and good on him. (William Booth and Hank Stuever, Washington Post, February 26, 2008)/We all contain multitudes, so if Mr.[Anderson] Cooper — who likes to work all the time and has another job on the side doing occasional stories for “60 Minutes”— wanted to take on another assignment, good on him. (David Carr, New York Times, November 7, 2011)