Here's the introduction:

SPOKEN: There's an old Australian stockman lying, dying. He gets himself up onto one elbow and 'e turns to his mates, who are all gathered around and 'e says:

One site I checked included this: Note: The next-to-last verse, which is rather offensive, but evidently was acceptable in Australia in the early 60s, refers to Abos, or Aborigines. Roughly, the American equivalent would be "darkies".

Some sites had "Lew" rather than "Bruce" for that verse. One changed it from "Abos" to "wombats," another left out the verse.

At this point, my guess would be that the meaning of "Let me Abos go loose" would be "dismiss my field hands." I see it as similar to saying "his employer let him go," meaning he was fired.