Most of the 'CB' monitors one sees in the classifieds are 'captive born' rather than 'captive bred'. That usually means they were hatched from eggs received from wild-caught, gravid females, rather than actually bred in captivity. There have been some interesting articles online recently about many of the Indonesian monitor 'farms' being exposed for just being a front for selling wildcaught animals, rather than an actual animal-breeding facility. I don't think many people were surprised by that. Here's an example of one paper covering a small number of companies selling a handful of species;
www.traffic.org/species-reports/traffic_species_reptiles26.pdf

melinus may or may not be an easy species to breed, but I've yet to see anyone post photographs of mating pairs, gravid females, eggs and hatchlings emerging from eggs.