Zulip's hosted plans for corporate users have a similar model to Slack's -- there's a free plan with limited access to history, and a paid plan with full access

Zulip's hosted plans for corporate users have a similar model to Slack's -- there's a free plan with limited access to history, and a paid plan with full access to everything. Since you mentioned nonprofits, we provide free hosting for open source projects and free or highly discounted hosting (e.g. 15% price) for many other nonprofits. See https://zulipchat.com/for/open-source/ https://zulipchat.com/for/open-source/ for more details.