Hi, I was wondering to use mproj[0:6] for my chip, but it seems that those pins are reserved for the board. Is it possible for us to use mproj[0:6] for the I/O of my designed chip? Thanks.

Yes, you can. It just makes the testing more complicated; the FTDI chip (USB to serial) on the development board connects to pins 1-4 for communicating with housekeeping SPI (for example, to program the SPI flash in pass-through mode), and pins 5-6 for the UART. Pin 0 doubles as a debug pin for the VexRISC processor. I do not think that currently there is a way to prevent the VexRISC processor from paying attention to this signal, which makes it very hard to use for anything other than the processor debug. For the other pins, it's necessary to hold the FTDI outputs in high-impedance, but otherwise you should be able to use them. Also note that when your program configures pins 1-4 to anything other than use for the housekeeping SPI, you can no longer program the flash SPI in pass-through mode unless you both hold the chip in reset and power cycle it. If you are building your own test board, then you can work around those issues at the board level.