Here it’s important to differentiate and it’s not so easy to label Zulip as fully trade-free. 1. https://zulip.com/ is NOT trade-free. There are plans that one can subscribe to in the “cloud”: https://zulip.com/plans/#cloud and even in self-hosted version: https://zulip.com/plans/#self-hosted 2. However, there is a “free-community-plan” for certain groups of people (in education or non-profit for example): https://zulip.com/help/self-hosted-billing#free-community-plan

This is why one might label Zulip as trade-free for “Open-source projects, Research in an academic setting, such as research groups, cross-institutional collaborations, etc., Organizations operated by individual educators, such as a professor teaching one or more classes, Non-profits with no paid staff or Communities and personal organizations”. Maybe 3 block might be appropriate for that?