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.
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.
