RISC-V is simpler, and easier to implement. Instruction density is very good with the compressed extension, and is applicable to many niches, from in-order low power embedded cores, to high performance out of order desktop CPUs. We can expect marginal improvements over x86 and ARM across the board.

On the other hand, it is not finished. A number of extensions have yet to be frozen, and we're just beginning to see commercial processors (I mean, where the ISA is exposed to the end user. NVIDIA already uses RISC-V internally).

I believe you have to pay royalties for Arm while RISC-V is completely open source.

The royalties aren't generally a big deal, being something like 2%. It's other issues, like complexity or startup fees or flat out being unable to get a license.

This. The world would be different, and probably better, if Samsung, Apple and other third parties could make their own x86 processors.

What's the situation regarding this for Mill/VLIW?

VLIW in its pure form is old enough that anybody should be legally able to build an ISA based on that concept.

The Mill folks are heavily into patents for their tech: https://millcomputing.com/patents/. So besides Mill's general feasibility it depends on how they work those patents.