Yes, there are lots of open-source RISC-V cores. Tim Edwards of efabless has another talk about creating a RISC-V based ASIC SOC: https://www.youtube.com/watch?v=EsEcLZc0RO8 based on PicoRV: https://github.com/cliffordwolf/picorv32. PicoRV is part of the efabless IP offerings. The chips will have a PicoRV harness on them.