So sorry for your disappointment!
Because the cafe is a part of the Polish Library Building, we can only serve members of the Polish Library Building Association and their guests. Fortunately, becoming a member is quick, inexpensive, and it comes with huge rewards. There are several membership levels ranging from Full Membership to Friend of the Library. But if you can't decide which one you'd like, you can always get a one day membership for $1. Applications are available at the Cafe.
A dumb explanation.
Why is this café members only? If there was a place like this in the Polish neighborhood where I grew up, no one would ever go there! All the decent Poles would boycott such an elitist place. Our neighborhood was about community, and sharing good Polish culinary traditions with everyone.
Shame on you!