"Kookaburra" was copyright 1934, renewed 1989 by Larrikin Music, which bought the rights to the song from the estate of Marion Sinclair, who died in 1988. Sinclair never enforced her copyright, so many assumed it was in the public domain. When Larrikin went looking for unauthorized uses of song, they found many, especially charts of the music for flute.
In 2009, they launched a high-profile lawsuit against the writers of the Men at Work song "Down Under
," claiming the famous flute section in that song copied "Kookaburra." In February 2010, an Australian court ruled in favor of Larrikin, but later awarded just the company just 5% of "Down Under" royalties, retroactive to 2002. Larrikin got a lot of bad press for using one Australian classic to besmirch another; in 2014 they changed the name of their company to Happy as Larry Music Publishing.