Zulip
Ko e Zulip ko ha talanoa ma'u'anga fakamatala 'oku fakaava mo e polokalama fakakomipiuta 'o e fengaue'aki na'e fa'u 'e Jeff Arnold, Waseem Daher, Jessica McKellar, mo Tim Abbott 'i he 2012. 'I he 'aho ni, ko e taha ia 'o e ngaahi founga kehe 'o e ma'u'anga fakamatala ta'etotongi mo e fakaava ki he Slack, 'i he 60,000 'o e ngaahi tukupa 'oku tokoni'i 'e he kakai 'oku laka hake 'i he 1000.
‘Oku mahu’inga heni ke fakafaikehekehe’i pea ‘oku ‘ikai ke fu’u faingofua ke fakahingoa ‘a e Zulip ko e fefakatau’aki kakato-ta’etotongi. 1. 'Oku 'IKAI fefakatau'aki-ta'etotongi 'a e https://zulip.com/. 'Oku 'i ai ha ngaahi palani 'e lava ke lesisita ha taha ki he “'ao”: https://zulip.com/ngaahi palani/#'ao pea na'a mo e 'i he founga 'oku talitali 'e he tokotaha pe: https://zulip.com/ngaahi palani/#'a e tokotaha pe .-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?