Josef Prusa Accuses Bambu Lab of AGPL License Violation with Closed-Source Plugin

Josef Prusa, founder of Prusa Research, has accused Bambu Lab of violating the AGPL-3.0 license with its Bambu Studio software. Prusa claims that Bambu Studio uses a closed-source networking plugin that is essential for the software to function, effectively making it a single product split across two files to bypass the license. He argues that this violates the open-source social contract: "You take from the community, you give back to the community."

Prusa Research discovered the fork accidentally in 2021.

Prusa Research discovered the existence of BambuSlicer in 2021 when internal builds accidentally sent telemetry data to Prusa's servers. According to Prusa, Bambu Studio cannot operate without the networking plugin, and the plugin cannot function without Bambu Studio. He described the arrangement as "license-laundering" and stated that under the AGPL, it remains a violation. Prusa also warned that Chinese 3D printing software poses security risks due to Chinese laws that require companies to cooperate with intelligence agencies, including surrendering encryption keys and reporting vulnerabilities.

Prusa cited a five-law framework in China that mandates encryption key surrender and intelligence assistance. He noted that 3D printers are often located in R&D departments, prototype shops, defense suppliers, university labs, and hardware startups, where they sit next to new intellectual property. The slicer software, he said, has the same data and access as the user's computer. Prusa emphasized that the legal environment in China provides "no neutral exits" and that jurisdiction follows the company across borders.

Prusa acknowledged that enforcing the AGPL license has been difficult. He said, "A license without a viable enforcement path is, in practice, a suggestion." He noted that Bambu Lab has issued multiple apologies but continued using the networking blob. The situation escalated when Bambu Lab issued legal threats to a small developer who attempted to open the networking plugin. Prusa questioned why Bambu Lab would risk burning goodwill over the issue. Tom's Hardware reported on the allegations.