Mozilla has had the unusual situation of having an enormous revenue stream from Google. It is reasonable in that situation to build some adjacent things that support the mission. MDN is amazing, for example! Rust was too! I do feel Mozilla has lost its way, and I think it would be crazy to spend resources available to the Zulip Foundation on projects that don't directly advance Zulip or its community.

I think the question presupposes that we solve the hardest problem for a new non-profit: Funding. We would be very lucky if Zulip with 1% of Mozilla's funding; we could do so so much with that scale of resources.

The biggest risk to Zulip's ability to succeed over the next few years is not risk of spending time on side projects. It's risk of not having the financial resources even to hire remarkable people who want to take a big pay cut to work on Zulip.