Episode 185

Daniel Stenberg on the cURL project


June 16th, 2023

37 mins 25 secs

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About this Episode


Daniel Stenberg


Richard Littauer | Leslie Hawthorne

Show Notes

Hello and welcome to Sustain! The podcast where we talk about sustaining open source for the long haul. On this episode, Richard and Leslie are super excited to have as their guest, Daniel Stenberg, Lead Developer of the cURL project. Today, Daniel shares his journey of how he got involved with cURL, its development over the years, the community behind it, and funding the development. Our conversation also touches on the upcoming release of cURL, the future of cURL, Daniel’s desire to grow the project, the benefits of people to collaborate with and provide support, and the role of cURL in the broader landscape of internet protocols and digital infrastructure. Press download to hear more!

[00:01:24] Daniel shares the story of how he became involved with the cURL project.

[00:03:55] We hear about the community behind cURL and the number of maintainers involved. He mentions having over 1,100 commit authors in the current repository.

[00:05:29] The discussion shifts to funding cURL’s development. He tells us for the first twenty one years he had it as a spare time project while having a separate job.

[00:06:28] He explains the challenge monetizing a free software project but emphasizes the value he provides to customers in terms of support and expertise.

[00:08:40] Leslie raises the topic of Daniel’s positive and generous attitude despite giving away free software and not always receiving equal support in return. He explains as long as he has enough customers to sustain his work, he remains calm and relaxed.

[00:11:46] Daniel discusses the development of his mindset and how he acquired a positive outlook over the past 25 years. He attributes his confidence to proven success, test cases that validate code functionality, and feedback form the large install base of cURL.

[00:12:45] Richard asks Daniel about his plans for the future of cURL, and Daniel expresses a desire to expand the team and highlights the benefits of having additional people to collaborate with and provide support.

[00:13:56] Leslie takes the opportunity to promote wolfSSL, the company Daniel collaborates with to support cURLS’s growth and provide services to more users, and he explains why he’s working with wolfSSL.

[00:17:02] Richard raises the topic funding individual maintainers with the broader open source ecosystem, and Daniel acknowledges that his support contract model might not work for all projects, as it requires a certain project size, importance, and ecosystem.

[00:19:04] Security issues, particularly zero-day exploit is brought up, and Daniel emphasizes the significance of security and mentions that maintaining cURL involves devoting a considerable amount of time to fixing bugs, addressing support questions, and handling security concerns.

[00:20:32] We hear how cURL fits into the wider landscape of internet protocols and digital infrastructure. Daniel talks about the importance of maintaining backward compatibility in cURL, and how he sees cURL as a tool that enables users to transfer data over the internet effectively.

[00:22:53] We hear about Uncurled, which is a book by Daniel.

[00:24:32] Daniel tells us what many companies would rather not say, such as companies that choose not to disclose their support or donations to cURL. They prefer to remain anonymous and keep their contributions private.

[00:28:02] He acknowledges that extracting significant value solely from donations can be challenging and offering support contracts provides a way to generate more revenue and provide additional value to companies.

[00:29:19] What’s hard for Daniel? He attributes his optimistic and positive mindset to his personality and outlook on life, but he also mentions facing struggles.

[00:34:24] Find out where you can follow Daniel on the web.


[00:07:35] “My biggest way in is when my customers run into a bug. So, I have this weird incentive to not do it too good.”

[00:10:32] “When you’ve been around for a long time and you know if things go well, I can be around for a long time further as well.”

[00:21:24] “We haven’t done a breaking change in 16 years.”

[00:30:09] “The hard part is the humans, the community, interacting with others, all the cultures, languages, and people.”


  • [00:35:03] Leslie’s spotlight is The Swedish Internet Foundation.
  • [00:35:47] Richard’s spotlight is WC and Cat.
  • [00:36:10] Daniel’s spotlight is Valgrind.



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