Do my group members have to sign up or download Joinable?

Joinable provides native Apple iOS and Android applications, but Joinable ask works great as a Progressive Web App (aka, an app in your browser). Furthermore, group members receive notifications via text message or email and can clicks links in those messages to bypass the need for usernames or passwords. Without these "magic links," members would need to sign in, but we do not use passwords — instead we use a temporary code send by email or text message.