BambuStudio forked PrusaSlicer but didn't release source code

Josef Prusa says BambuStudio has violated the AGPL license by forking PrusaSlicer and distributing it without releasing their modified source code [Josef Prusa]. The AGPL requires that any derivative work of open-source software must also be open-sourced under the same license. BambuStudio has not done so, despite building its software directly from PrusaSlicer’s codebase.

BambuStudio’s software is functionally a rebranded version of PrusaSlicer with custom UI elements and workflow tweaks for Bambu Lab’s printers. Yet the company has not published the source for these changes, which Prusa considers a clear breach of AGPL terms [Josef Prusa]. Open-source licensing experts agree: if you distribute modified AGPL code, you must make the source available.

This case cuts to the core of open-source trust. Companies can use and modify open-source tools, but only if they give back. Bambu Lab benefited from years of community-driven development in PrusaSlicer, then commercialized a closed version without compliance. That undermines the reciprocity AGPL is designed to enforce.

The 3D printing community relies on open-source projects like PrusaSlicer for innovation. When companies take the code but ignore the license, it risks chilling contributions and centralizing control in proprietary hands. Other firms may now question whether open-sourcing their tools invites free-riding.

No legal action has been confirmed yet, but Prusa’s public statement signals he’s prepared to defend the license. How Bambu Lab responds—open the code or fight—will set a precedent for how strictly open-source licenses are enforced in hardware-adjacent software.