Is Asymmetric two way ranging algorithm free to use or do one need to purchase license from decawave?

Recently i came across patent document of decawave in which they have claimed on asymmetric two way ranging algorithm mentioned below

Although the same algorithm is readily available with opensource projects

Hence I am confused whether this same algorithm can be used for commercial development of products for free or do one need to pay licensing fee to use them ?

Patents are made for protection. If you are using DW patents for Decawave chip, why should they chase you? Also why not ask Decawave grant you use the patent for your project, why not?