I needed to burn a DMG to a DVD-DL disc without having access to a working Apple computer. Over the process of trial and error and found this to work pretty well.

Required Items
  1. dmg2img-1.6.5
  2. DMG Image
  3. DVD-DL burner
  4. Blank DVD-DL disc


Step 1: Manually build and install dmg2img-1.6.5
You'll notice that if you use aptitude that the current version of dmg2img in the repository is 1.6.2. We need to install the updated version. I am researching ways to update the respository version.

Step 1.1: Download source code for dmg2img-1.6.5: http://vu1tur.eu.org/tools/
Step 1.2: Prepare build environment
Code:
sudo apt-get install build-essential gcc zlib1g zlib1g-dev libghc-zlib-dev libbz2-dev
Step 1.3: Extract archive, build source, install binary
Code:
cd ~
Code:
cd Downloads
Code:
tar -xf dmg2img-1.6.5.tar.gz
Code:
cd dmg2img-1.6.5
Code:
make
Code:
sudo cp dmg2img /usr/bin
Step 1.4: Verify correct version is installed by running dmg2img
Code:
dmg2img
dmg2img v1.6.5 (c) vu1tur (to@vu1tur.eu.org)

Step 2: Convert DMG to IMG using dmg2img-1.6.5
Code:
dmg2img in.dmg out.img
Here in.dmg is the name of the DMG that you need to convert
Following this process you should have out.img
Note: I tried to mount the img in various ways but it did not work. I still went ahead with the burn.

Step 3: Burn IMG file to DVD--DL using K3b
Code:
sudo apt-get install k3b
Start K3b: Sound & Video > K3b
Open the IMG file and burn!