Did you find solution for this problem ??
I've the same problem, how can I preflashing the NAND controller for linux like the "NX2LP NAND Programming Utility" ??
You can build firmware with SDCC, although I don't believe it is source compatible with Keil.
There is also http://sourceforge.net/projects/fx2lib/develop which has helper routines for various things.
You can use libusb to send commands to your device - I use it as well as the python bindings for testing.
This is late for this thread, but this guy ported some of the samples for the Keil compiler to SDCC and Linux: www.danielclemente.com/placa_pi/index.en.html#toc18
We don't have the funds for the Keil compiler so I'm working with SDCC in Windows. My firmware is based on his code and it is mostly working. Still one bug...