I wish I could tell you that your Mac is compatible with the LG GE20 20X DVD Burner but unfortunately it is not.
Here are the system requirements for this burner LG GE20 20X DVD Burner Technical Specifications
The CD included is not the only item that is not compatible with the Mac, it is also the DVD burner itself. It is only windows compatible I'm afraid.
However, I do know that the Apple.com online store, has a comparable DVD+RW burner, theLaCie 22x d2 DVD+RW with LightScribe
which will work with your iMac.
This is a genuine incompatibility issue.
If you had an Intel iMac, there actually is a workaround process where virtual machine software, like VMWare Fusion or Parallels, could be installed, with a version of Windows XP, Vista, or 7, display as a 2nd terminal within a Mac OS X desktop.
What's makes this effective, is that the LG GE20 could work with a windows virtual machine and because software like VMWare for example, can share devices, including optical CD/DVD drives, the Mac could share that drive with the windows virtual machine.
But since you do not have an Intel iMac, unless I am reading the description of your Mac computer(Apple iMAC Mac Notebook) incorrectly, the LaCie burner information, I provided above, would be the best option for your model of iMac.
Again, if I have described your model of Mac incorrectly let me know and I will be glad to assist further.