Watabou explicitly says you can use the maps, and DMDave openly notes that he’s using Watabou generated maps on his page. DMDave also added content beyond the maps.
I’m curious to know what your problem is with maps genrated by this getting used in a commercial product? Would you feel the same way if he paid for maps? Would you feel the same if he used Dyson’s commercial maps, which are also free to use?