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At FOSSY 2026, several people from the Software Freedom Conservancy (SFC), which organizes the conference, gave a presentation about an ongoing violation of the Affero General Public License version 3 (AGPLv3). Bradley Kühn, Karen Sandler, and Denver Gingerich spoke about different aspects of the violation, which is in regard to 3D-printer software from Bambu Lab, and what is being done to try to provide users with alternatives. One aspect that is particularly interesting is that the circumvention that the company is employing is precisely what the AGPL was written to prevent.
Kühn began the session by noting that he has been an activist in the free and open-source software (FOSS) communities for over 30 years and that " this moment in history [...] has more activism opportunities than I have seen in my career ". In the past, he and his colleagues have been triaging disasters of various sorts but over the past six to eight months they have been triaging opportunities instead. Sandler added that the opportunities being offered are difficult; " it's not like people are saying 'would you like this money or that money?' ".
The opportunities he is describing are not really about money, Kühn said, but provide ways " for activists to get stuff done and to engage people ". Over the past six months or so, SFC has successfully engaged with " an entire community of enthusiasts ", which only had a passing familiarity with FOSS, on a multitude of freedom-centric topics: " free software, free culture, free creation ". That is exciting, but he was getting ahead of himself because that is where the story ends, so he wanted to go back to the beginning.
Backstory
Some time ago, 3D printing was invented, which is something that he watched from afar; a breadboard fire when he was an undergraduate convinced him that he should be a software-only person. He is a fan of the 3D-printing culture, and enjoys the talks that come from it, but he does not participate. As part of the license-violation investigation, he and Gingerich did a crash course in the history of 3D-printing, though Gingerich already had much of the background.
Kühn related some of what he learned, including that the hobbyist 3D-printing field started out as a curiosity. People who wanted a 3D printer had to build one themselves, since there were no already assembled devices on the market. Some of those who built the early printers went on to found companies that now sell 3D printers, which is a key element in the development of the community. Like Linux, 3D printers started as a hobby and remained " a hobby for a long-enough period of time that the hobby culture could not be immediately eradicated by venture capitalists ".
The " wonderful thing " about 3D printing is that the people developing the software needed to run the devices looked to the free-software community and " thought twice " before they started picking licenses for their code. An important piece of the tooling needed to use these devices is a program known as a "slicer", which turns a 3D model—some slicers also help build these models—into thin 2D slices that can be converted into the language that the printer hardware understands. He likens that language to assembly language, which is an oversimplification, but helps provide a conceptual framework for him.
A longtime free-software enthusiast, Alessandro Ranellucci, created a slicer, which he called "Slic3r". Kühn said that his only criticism of Ranellucci was his choice of the name, which makes it hard to distinguish between the program and the overall type of program in a talk, so Kühn used "slicer with three" to distinguish them. The two spoke over a video chat and Ranellucci said that he chose the AGPLv3 for Slic3r to try to avoid the mess with Bambu Lab: " I anticipated all this, because my biggest worry was that someone was going to do 'Slic3r as a service' ".
While there are 3D printers that use other slicers, it is difficult to find one that is not best used with some fork of Slic3r, Kühn said. There are around 18 active forks, but the most well-known is PrusaSlicer. It came about because a friend of Ranellucci's, Josef Prusa, saw 3D printing as not only just a business opportunity, but " a free-software business opportunity ". Prusa built a company based on providing customers with printer plans, free software, free firmware, and so on, Kühn said; that company was the dominant player in the market for a time.
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