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

Hac de causa quis titulus Zulip quasi commercium liberum pro "inceptis Open-fontis, Inquisitionis in ambitu academico, ut in investigationibus sodaliciis, cooperationibus crucis institutis, etc., Instituta per singulos educatores operata sunt, ut professor docens unam vel plures classes, non-commodis sine baculo vel communitatibus et institutis personalibus". Maybe 3 obstructionum might be appropriate for that?