Opening dmg files

[Quartz]

A little late to the party here, but a mac DMG is kind of like ISO 
except with more stuff bolted on. DMGs have native support for multiple 
partitions (including boot sector stuff), compression, encryption, 
sparse support, etc. Wikipedia has some info on the structure of the 
file and ways to open/mount it on Windows and *nix: 
https://en.wikipedia.org/wiki/Apple_Disk_Image

If this guy's instructions say "play it in a software dvd player" then 
it sounds like what he did was just naively image a DVD without 
understanding that the resulting file was mac proprietary. It's probably 
a just UDF formatted 'raw' dvd rip with a bunch of VOBs.