RISC-V is not an IP core, just an instruction set architecture.
Any implementation of it has the exact same patent minefield to navigate as any other ISA. Most of the patents are around implementation techniques not instruction set.
The RISC-V instruction set was carefully designed not to require the use of any currently valid patents to do an implementation. It is up to each processor designer to not violate any patents in their project.
this is unfortunately not true (that the RISC-V ISA was designed not to require currently-valid patents). people may believe that to be the case, but it's not. from 3rd hand i've heard that IBM has absolutely tons of patents that RISC-V infringes. whether IBM decide to take action on that is another matter. they're a bit of a heavyweight, so there would have to be substantial harm to their business for the "800 lb gorilla" effect to kick in.
Of course, the various extensions might violate current patents (I would guess that packed SIMD and cryptography extensions are particularly at risk). But the basic ISA does not use anything that was not already widely adopted by 2003.
It's not actually possible to do this though, it's up to the other side's lawyers to decide if they're going to sue you, and the answer is yes if they can afford it. You don't have a jury on hand to evaluate every patent that ever exists.
Besides that, engineers in large companies are told to explicitly not look up any patents so they won't be accused of willful infringement.
I did not mean to imply that RISC-V implementations are patent/royalty/license free, only that the spec is. Not having to define a spec of your own is a significant time and money savings.
Any implementation of it has the exact same patent minefield to navigate as any other ISA. Most of the patents are around implementation techniques not instruction set.