You can probably use pretty much any software that allows you to edit either an AVI, or DVD in its entirety that allows you to do a PiP(Picture in Picture). I know Ulead, Pinnacle Studios, Sony Vegas, CyberLink PowerDirector, and programs like those allow you to do it.
I used an animation program to create a logo avi clip and when i use Ulead dvd workshop to build my dvd's i add it as the "play this first" clip before a menu appears hope this helps es