The RISC-V ISA is free and open with a permissive license for use by anyone in all types of implementations. Designers are free to develop proprietary or open source implementations for commercial or other exploitations as they see fit. RISC-V International encourages all implementations that are compliant to the specifications.
Note that the use of the RISC-V trademark requires a license which is granted to members of RISC-V International for use with compliant implementations. The RISC-V specification is based around a structure which allows flexibility with modular extensions and additional custom instructions/extensions. If an implementation was based on the RISC-V specification but includes modifications beyond this framework, then it cannot be referenced as RISC-V.