[m52go]

Open-core, or fully open-source with paid offerings (e.g. Zulip -- see tabbott's comment below [0]).

Let the DIYers host their own instances, but offer support and/or on-premise deployments for a fee. It seems to be what Mattermost, Zulip, and others are doing with some success.

Mattermost also includes use of their mobile notification relay servers in their paid offerings, which is compelling, because otherwise you have to build and distribute your own mobile apps.

[0] edited to include reference to important comment

[tabbott]

Just to be clear, Zulip is not Open Core. We are 100% open source software, in contrast with Mattermost, GitLab, and many (most?) other VC-funded applications marketed as "open source".

I think this is a really important distinction; the VC-funded open core business model has a fundamental incentive structure that pushes the company to makes its open source project an intentionally crippled demo product so that they don't miss any revenue they might have had as a proprietary product.

[m52go]

Thanks for clarifying -- I've edited my comment to make that more clear. And thanks for your work on Zulip!