This is not an open and free CPU. It just implements the open and free RISC-V instruction set. Judging by the SiFive business model they will in the future inevitably add proprietary extensions.
Hantro and panfrost fill this gap. No blob is required afaik.
While very cool, open source drivers for propriety a proprietary gpu design is not quite the same as open silicon or open gpu isa, which is what I think the parent was asking for.