Licenses are a way to prevent people from overfishing populations. Certain populations have been overfished to the point of being endangered, and if a species gets erased out of an ecosystem, the overlying ecosystem gets thrown out of place depending on how key of a species the fish was.
There are some species the gov does not care about eg the invasive lionfish and asian carp
You could maybe sub half the doubianjiang with low sodium miso, its not an exact subsitute but i figure it’ll still provide that strong flavor you want