You could also take a look at ARToolkit
http://www.hitl.washington.edu/artoolkit/ for ideas.
Even thought they state that ARToolkit is GPL it is in fact not they violate the GPL
Quote:
IMPORTANT NOTICE REGARDING YOUR RIGHT TO USE ARTOOLKIT:
ARToolKit is made available freely for non-commercial use under the GNU General Public License. Commercial licenses to a professional implementation of ARToolKit are available for users for whom the GPL is not suitable, or who require a higher level of support, or who require customization or other specialist modifictions. Commercial licenses are administered by ARToolworks, Inc., Seattle, WA, USA. Click here for more information on ARToolKit licenses and your usage options.
This is the violation: "freely for non-commercial use"
There understanding of non-commercial use and the Freesoftware foundations understanding differ.
Plus they claim exclusive rights to they Augmented Reality Technology via patents. Along with half a dozen others lol.
I am currently trying to prove Augmented Reality as prior art.