Before progressing to the next subtopic, I would like to add one further point of clarification that was requested by "Yeshivish" in his comment on the previous post. If the גר"א and מהרש"ל agree with the ב"ח that cooking and benefiting from mixtures of עוף and חיה is forbidden because these substances are Rabbinically included in the category of בשר, then why don't they agree with him in extending the prohibition to non-kosher species of meat/milk as well?
The answer is as follows: There are three ways in which we can understand the Rabbinic "inclusion" of עוף and חיה in the framework of the prohibition of בשר בחלב:
1) The Rabbis did not change, extend or modify the categories of בשר or חלב as defined by the Torah. They simply decreed a totally new, separate prohibition on eating עוף or חיה with milk in order to prevent misunderstanding, confusion and possible violation of Torah Law. This is the view of the majority of פוסקים, including the שלחן ערוך.
2) The Rabbis expanded the definition of בשר to include חיה and עוף, and expanded the definition of חלב to include the milk of חיות. Hence, these mixtures are considered full fledged בשר בחלב מדרבנן and may not be cooked, eaten or benefited from. However, there was no reason to extend this decree to non-kosher species of meat/milk, since they are already forbidden for consumption anyway. This is the view of גר"א and מהרש"ל.
3) The Rabbis didn't expand the definitions of meat or milk to include new species, such that we would have to "justify" applying their decree to non-kosher species. They simply "removed" the requirement that meat/milk come from a particular list species in order to qualify for the prohibition. Ipso facto, (or, as we would say in Talmudic parlance, ממילא) this means that ALL combinations of meat and milk - including עוף, חיה and even non-kosher animals - are now defined as בשר בחלב מדרבנן with all the implications that emerge therefrom. This is the position of the ב"ח.