For the record, my submission of the article above doesn't mean that I think Poland is not liberal in any way (I'm Polish by the way). I just found the article pretty in-depth and interesting thus worthy of posting here.
Thanks a lot for posting this, I had never encountered Poland in history classes (French edu system) except for the 20th century history parts, and had no idea about either the Union in itself or its political system. We heard a lot about the Italian quattrocento, as it lead up to the French Renaissance, but of what was happening in Poland, not a peep. In the same fashion, we didn't hear that much about even the holy German empire, as history in France is taught in a very French-centric way from the fall of the Roman Empire up to the 1st world war. I think it would do us a world of good to approach history in a more global fashion, paying less attention to rote learning of chronologies, and hearing more about the stories of ideas and peoples throughout the ages.
It's interesting for me (as a Pole), but for the opposite reason to the author - I'm interested in the parables to Polish history he found looking from angolsaxon protestant POV. I was aware of some of them (Magna Carta, Habeas Corpus), but not all.