Open source software explained by FFmpeg & VLC developers | Lex Fridman Podcast
Developers of FFmpeg and VLC explain open source software, comparing it to sharing a recipe along with instructions to build the oven and permission to modify and resell it. They discuss the spectrum of open source licenses from permissive (MIT, BSD) to copyleft (GPL, AGPL), and the real-world challenges of relicensing a project that has thousands of contributors — including tracking down a factory worker whose deceased son had contributed code.
Summary
The conversation opens with FFmpeg and VLC developers explaining open source software using a chocolate cheesecake analogy: proprietary software gives you the finished cake, while open source gives you the cake, the recipe, instructions to build the oven, and permission to modify and resell it. They emphasize that software is essentially a very long recipe of instructions, and that open source enables large global communities to collaborate — FFmpeg has had 2,000–3,000 contributors and the Linux kernel around 10,000.
The discussion moves into open source licensing, explaining that licenses fall into two broad categories: permissive licenses (MIT, BSD, Apache) which allow almost any use with minimal conditions, and copyleft licenses (GPL, AGPL, LGPL) which require that modifications be shared back with the community. The speakers describe the license as a 'social contract' in the Rousseau sense — the one thing the community agrees on, and the foundation that allows forking and merging (e.g., KHTML → WebKit → Blink).
A significant portion covers the relicensing of libVLC's core from GPL to LGPL. The motivation was twofold: to allow commercial companies (like game developers) to embed VLC without being forced to open source their entire application, and to comply with Apple App Store terms that made GPL apps difficult to distribute on iOS. The speaker describes the enormous effort required to relicense — contacting over 350 contributors individually, sometimes traveling in person to find them. One particularly emotional moment involved visiting a factory worker to obtain permission to relicense code written by his deceased son, illustrating how deeply personal open source contributions can be.
The conversation concludes with reflections on the diversity of the open source community — spanning people in war zones, introverts of all backgrounds, and contributors from every walk of life. The speakers stress that the community is meritocratic and judges contributions purely on code quality, regardless of the contributor's employer, nationality, or status.
Key Insights
- The speaker argues that the open source license functions as a 'social contract' in the Rousseau sense — it is the one thing the community agrees on, and it enables forking and merging of projects, as seen with KHTML evolving into WebKit and then Blink.
- The speaker explains that relicensing VLC's core (libVLC) from GPL to LGPL required personally contacting over 350 contributors, including traveling in person to find some of them — in one case approaching a factory worker whose deceased son had written the contributed code.
- The speaker notes that LGPL (Library GPL) was strategically chosen for libVLC so that commercial companies, such as game developers, could embed VLC to play video without being legally required to open source their entire application.
- The speaker points out that Apple App Store terms of service make it very complex to distribute GPL-licensed applications on iOS, which was the second major reason for moving VLC's core to LGPL, with the iPhone and Apple TV versions ultimately using the Mozilla Public License (MPL).
- The speaker argues that the FFmpeg and VLC communities are purely meritocratic — code is judged solely on quality, and being an engineer at a large well-known company carries no weight; patches get rejected if they don't meet standards regardless of the contributor's background or employer.
Topics
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