It comes out of the box with Linux in the eMMC and FPGA programming that connects the CPU cores to the peripherals, so if all you want to do is run RISC-V Linux

It comes out of the box with Linux in the eMMC and FPGA programming that connects the CPU cores to the peripherals, so if all you want to do is run RISC-V Linux then you don't need to muck about with FPGA programming. But you can, if you wish, rebuild the default FPGA programming from source code, enhance it, or replace it completely.