I am building hardware using the MRF24J40MA. So far I have only looked at the software.
Use a microchip C compiler. Porting the code would be a royal pain. There is an off chance that you can link to the stack but I so not expect it.
Only specific microchip processors are supported. The easiest way to see this is to download the software and run Zena which configures the code/stack.
Study the Microchip ZigBee stack doc's and you will see that user code communicates with the stack with a very small set of functions.
I get the impression that this is not a plug and play process. The microchip forum has posts about various problems that pop up. This is not a well worn path and finding help may be difficult.