It's not. It can be. I'm not proud of it. I'm more familiar with rpm tbh and I just hacked the deb together several years ago, forgot how I did it and have to tweak it every time the Makefile gets updated and have to update the quilt stuff.
If anyone out there is an official debian packager who'd like to do the packaging "properly" and make kplex available in normal repos let me know. Frederic I can let you have the deb source today privately or put it up on the web site sometime in the next couple of days