Hi Radha,
welcome to our forum.
To your questions:
1. Disko is written to function ontop of X11 or the Kernel Framebuffer. The Beagleboard ships with a Kernel utiliziing the OMAP DDS2 framebuffer driver. We have a little howto to describe the configuration
here.
2. Disko is a graphics framework located somewhere between DirectFB and QT. Applications that want to utilize disko, have to use at least the disko drawing routines. Just like porting a GTK application to QT.
Do you have a specific application in mind that you want to port?
kind regards
Stefan