Guys, I think you'll find that it's a fairly regular event in Darwin (and some other places too) to have one company sub-contract out a charter or part of a charter to another company.
Sure is, I did my fair share of airport tarting around Darwin a decade ago.
Where it got (gets?) really murky though, is when as a charter pilot with a charter maintained aircraft with a charter AOC only you get subcontracted in to do the RPT run to YBTI....