[naraic0o]

I think you mean RISC-V (V being the Roman numeral for 5).

The MIPS ISA is now also open source, as of Q1 2019[0].

[0] https://www.mips.com/mipsopen/

[sanxiyn]

Note that this is MIPS Release 6, which is incompatible with existing MIPS ISA. For example, Debian is planning to create an entirely new port, mipsr6, in addition to mips.