Peer Richelsen

Things Peer Says on Podcasts

Co-founded and chairs Cal.com, the open source scheduling company, and spends most of his public commentary on the security and trust problems open source software is running into as AI accelerates code generation and contribution. His argument, made on The Changelog, is that AI has flattened the barrier to both building and attacking software, and that the manual reporting culture that used to catch problems in open source is being drowned out by AI-generated noise. Before Cal.com, he was head of product at On Deck and founder of Lean Hire, and went through Y Combinator. He shows up mainly through Cal.com's own channels and as a guest on developer-focused podcasts like The Changelog, where he discussed Cal.com's decision to fork its own codebase and move sensitive parts closed source.

Where to Find Them

Peer Richelsen has been a guest on Open Source Startup Podcast and The Changelog .

Recently: “Forking Cal.com to closed source (Interview)” on The Changelog (September 2026); “E8: Open-Sourcing Business Applications; Calendso's Story” on Open Source Startup Podcast (September 2021).

What They Said

“My theory is that the majority of open source repositories are compromised right now. We just don't know yet.” — Peer Richelsen, The Changelog

Richelsen had just explained that Cal.com went open source partly to build the most secure codebase it could, and that until early this year he would have said flatly that open source is always more secure than closed source. He says he no longer believes that. He points at Firefox's open P0 vulnerabilities as the illustration: if a project that well resourced looks like that, most repositories are worse.

The Changelog · 2026-09-03 Permalink → Listen →
The Changelog Around 14:58 into the episode
Peer Richelsen

And

Adam Stacoviak

…that we think are worth fixing. We're happy to hear your ideas. We want you to use Swamp, but it's issue-based co-contributions. And you'll give us the problem or the challenge or the solution in prose. And they may even bring that into context behind the source. And they may even write a problem.

Peer Richelsen

…find and abuse vulnerabilities has like a hundred X in terms of ease of use, right? And so you're giving basically evil people a single prompt in their terminal to find and abuse open source repositories. So, the whole pendulum of like, oh, we're open source, we're more secure, has completely swung in the other direction where it's like, wow, this is so easy to hack any open source repository. My theory is that the majority of open source repositories are compromised right now. We just don't know yet.

Adam Stacoviak

Firefox

Peer Richelsen

has Firefox. Firefox has 12 P0 vulnerabilities. Like, what do you think your open source repository is looking like? You know?

Adam Stacoviak

Yeah, that's funny.

Speaker names come from our own diarization. The position is estimated from where the line sits in the episode.

Collections They Appear In