The answer to the question "Is X patent-free" can never be yes until all possible patents have expired. I don't think it's really even possible to do much more than what AV1 is doing. Any patent known was avoided or is royalty-free.
> To fulfill the goal of being royalty free, the development process requires that no feature can be adopted before it has been confirmed independently by two separate parties to not infringe on patents of competing companies.
> [...] technology contributors license their AV1-connected patents to anyone, anywhere, anytime based on reciprocity (i.e. as long as the user does not engage in patent litigation). As a defensive condition, anyone engaging in patent litigation loses the right to the patents of all patent holders.
> As an additional protection for the royalty-free status of AV1, the Alliance has a legal defense fund to aid smaller Alliance members or AV1 licensees in the event they are sued for alleged patent infringement.
