I don't see a description of their solver on their website at the moment, and my French is no good... If you really want your solving rules to match the "dCode" version exactly, you'll have to figure them out somehow - ask the people who wrote them, figure them out experimentally, ... in that respect my crystal ball is not any clearer than yours ;-)

Remember, the "rules" for solving the puzzle are not necessarily the same as an algorithm. The rules will, in English (or French?), say things like "longer words match first", "the search proceeds from left to right, top to bottom", "each word matches only once", "matches across have higher priority than diagonal", etc. Maybe if you ask the people who implemented the solver, they can give you these rules, without revealing their code.