The Challenge of Maintaining Curl

Summary

By Jonathan CorbetAugust 29, 2025 OSS EU Keynote sessions at Open Source Summit events tend not to allow much time for detailed talks, and the 2025 Open Source Summit Europe did not diverge from that pattern. Even so, Daniel Stenberg, the maintainer of the curl project, managed to cram a lot into the 15 minutes given to him. Like the maintainers of many other projects, Stenberg is feeling some stress, and the problems appear to be getting worse over time. Curl, he began, is "a small project with a big impact". It began in 1996 with all of 100 lines of code; it has since grown to 180,000 lines that have been contributed by 1,400 authors. In any given month, there are 20-25 developers who are actively contributing to curl. The project has exactly one full-time employee — that being Stenberg himself. The program is widely used, having been deployed in at least one-billion devices. Just about anything that occasionally connects to the net, he said, uses curl to do it. But using curl is different from supporting its development. As an example, he put up a slide listing the 47 car brands that use curl in their products; he followed it with a slide listing the brands that contribute to curl. The second slide, needless to say, was empty. (A version of both slides can be seen on this page). Companies tend to assume that somebody else is paying for the development of open-source software, so they do not have to contribute. He emphasized that he has released curl under a free license, so there is no legal problem with what these companies are doing. But, he suggested, these companies might want to think a bit more about the future of the software they depend on. Open-source software is the best choice, he said, but maintaining it is a tough job. Most projects out there have a single maintainer, and that person is often doing the work in their spare time, without funding. Maintenance involves a lot of tasks, including taking care of security, reviewing patches, writing document...