Bambu Lab and the AGPLv3 Violation: How a Chinese 3D Printer Maker Skirts Copyleft

At the FOSSY 2026 conference, Bradley Kuhn, Karen Sandler, and Denver Gingerich of the Software Freedom Conservancy (SFC) presented a talk on the ongoing AGPLv3 license violation by 3D printer maker Bambu Lab. According to Kuhn, over the past six months the story has gone from “dissecting yet another disaster” to an opportunity: a whole community of enthusiasts, previously only passingly acquainted with free software, has rallied around the topic.

Background

Hobbyist 3D printing, like Linux, stayed a hobby long enough that “the venture capitalists couldn't destroy it instantly.” The key tool here is the slicer, a program that slices a 3D model into thin layers and turns them into commands the printer understands. The enthusiast Alessandro Ranellucci wrote the Slic3r slicer and deliberately chose the AGPLv3 for it, foreseeing the danger: “I was afraid someone would make Slic3r as a service.” The best-known fork is Josef Průša's PrusaSlicer.

Enter Bambu

During the pandemic, China's Bambu Lab entered the market, and by 2025 it held 38–48% of the segment of printers priced at $500–3,000. The company needed a slicer — and it began shipping a modified PrusaSlicer under the name Bambu Studio, at first with no source code at all. Under pressure from the community, the source code was released, but, as is usually the case, not in full compliance.

The gist of the trick is this: Bambu Studio offers to “download” additional components — two .so files that are loaded dynamically via dlopen(). This thin shim reaches out over the network to a large application on Bambu Lab's servers, passing a “key” — a fixed User-Agent string, identical for all clients. The company declared this User-Agent to be an anti-circumvention mechanism under the DMCA. But, as Kuhn stressed, this is exactly what the AGPLv3 forbids: you cannot move part of an Affero-GPL application onto a server and keep it proprietary.

Poland's Paweł Jarczak reverse-engineered the network code, for which he received a DMCA notice from Bambu Lab — “GitHub, of course, honored it, because Microsoft.” Jarczak continues to maintain OrcaSlicer, mirrored in the SFC's baltobu project. Gingerich added that Bambu Lab is also violating the GPLv2: the printers' firmware uses a Buildroot-based Linux, but no source could be found for the 300-megabyte image.

What's next

The SFC is betting not only on the courts (as in its case against Vizio, based on contract law) but also on reverse engineering by the community — that's faster. The campaign's fundraiser exceeded its goal of $250,000, and the organization can now hire an in-house lawyer. Sandler urged buyers to demand the complete source code for their devices: a disgruntled YouTube video or a Reddit thread is also a form of license enforcement. After all, a license is not “magic pixie dust” in itself: until someone's “feet are held to the fire,” no one will bother to comply.

Source: Hacker News