Are there legal issues that make it more favourable?
IMO, compared to OpenSPARC, this is a fresh design that leverages lessons learned from everything that proceeded it. There are many problems with SPARC that makes it hard & expensive to scale up and down.
And yes, the RISC-V ISA is simpler than the SPARC ISA. We also have clearly separated the base integer ISA from the various extensions, such as floating-point, atomics, supervisor, etc.