Everyone in EU-countries can apply to university in Poland in the same way as Poles. If you apply in this way there will be no tution fee. The studies will be in Polish of course. There are also English Divisions (eg. medicine) at several Polish universities, where the studies are in English. In this case you pay a tution fee. But due to some law you can't study at this English Divison if you have Polish citizenship.
I guess people outside EU can apply for university in the same way, but they need legal permission (visa) to study in Poland.
