Zulip was originally developed by Zulip, Inc., a small startup in Cambridge, Massachusetts. Zulip, Inc. was founded by the MIT team that previously created Ksplice, software for live-patching a running Linux kernel. Zulip was inspired by the Barnowl client for the Zephyr protocol, and the incredible community that Zephyr supported at MIT.
Zulip, Inc. was acquired by Dropbox in early 2014, while the product was still in private beta. Zulip's beta users loved Zulip's unique user experience and continued using it, despite the fact that the product was not being actively developed. After a year and a half, Dropbox generously decided to release Zulip as open source software so that Zulip's users could continue enjoying the software.
As a result, the first time the public had the opportunity to use Zulip was when Dropbox released Zulip as open source software in late 2015. The open sourcing announcement was very popular, staying at the top of both Hacker News and the programming subreddit for an entire day.
Zulip was open sourced with the complete version control history intact because 10 Zulip users visited Dropbox for a full week to help with the technical work. The Zulip community is incredibly grateful to both Dropbox and those enthusiastic early users for making the Zulip open source project possible.
Success as an open source project
At first, the Zulip open source project was maintained with just a bit of lead developer Tim Abbott's nights and weekends. However, the community steadily gained new contributors, and has now grown to be one of the world's largest and most active open source projects. We highlight a few milestones below:
- By the end of 2015, the open source project was already going strong with a community of dozens of developers around the world.
- At the PyCon Sprints in May 2016, dozens of developers got involved in contributing to Zulip; a major accomplishment from those sprints was annotating Zulip with mypy static types.
- By late 2016, more than 150 people from all over the world had contributed almost 1000 pull requests to the software, and the Zulip project was moving faster than when the original startup employed 11 full-time engineers.
- At the PyCon Sprints in May 2017, tens of Zulip core developers gathered and led the largest PyCon sprint ever, with over 75 developers contributing to Zulip over course of the 4-day event.
- As of October 2018, the Zulip server project had merged 6500 pull requests written by over 400 developers.
In 2016, Tim Abbott started a company, Kandra Labs, to steward and financially sustain Zulip's development. Kandra Labs was soon awarded a large grant from the US National Science Foundation, and also acquired additional sources of funding.
In mid-2017, Kandra Labs launched two products: a hosted Zulip service at zulipchat.com, and an enterprise support product for on-premise deployments.
As of October 2018 the hosted service was seeing 4x year over year growth in daily active users, and the on-premise product was seeing rapid adoption (fueled partly by the sunsetting of HipChat server).
Kandra Labs is supported by nearly $1M in SBIR grants from the US National Science Foundation, and Zulip has benefitted enormously from the 30+ developers that started working on Zulip via Google Summer of Code and Google Code-In.