I was having trouble with using kernel 2.6.21 that get supported by default UrU kernel, the X server refused to run. So, in my despair, I view some LKML threads, patch here and there: Voila! I got a working  Kernel driver for U.r.U fingerprint for Linux kernel 2.6.31. [NOTE: Remove the .pdf extension.]This patched driver has been working in Debian’s 2.6.31-trunk and Ubuntu Karmic, my fave distro at the momen. The installation is simple and described here.For the sake of KISS, I will try to cover it for you.

$ mv dpfp-2.6.31.tar.gz.pdf dpfp-2.6.31.tar.gz
$ tar xvfz dpfp-2.6.31.tar.gz
$ cd source
$ make

And then install it to your kernel:

$ sudo mkdir /lib/modules/`uname -r`/kernel/drivers/biometric
$ sudo cp mod_usbdpfp.ko /lib/modules/`uname -r`/kernel/drivers/biometric/
$ sudo depmod -aq

Then you can abuse it the way you feel. This kernel has been tested worked on UrU 4500 and UrU4000B.