Texting friends

Hey y’all, I recently made friends with someone from the BFF app. We met up and afterwards they gave me their partner’s number. Now I text them both separately. They told me they are polyamorous. I am in a committed monogamous relationship and explained that I only want to be friends. They said they’re just looking for friends on the BFF app and use another app specifically for poly dating. I hung out with my friend and her partner 3 times now. Last week my partner joined us too. Afterwards my new friends brought up the possibility of creating a group chat with both couples. I think it could be fun… but is this normal?