PSA: Elegoo Centauri Carbon & GPL Compliance

📌 The Issue

The Elegoo Centauri Carbon 3D printer uses a heavily modified version of Klipper firmware, specifically based on a commit 616 commits past v0.9.1 (shorthash 28f60f7e). Klipper is licensed under GPL-3.0, which legally requires all modifications to be made publicly available.

          Why this matters: GPL compliance isn't optional—it's
          a legal requirement. When companies use open-source software, they
          must respect the licenses. This ensures transparency, security, and
          the right for users to modify and improve their own devices.
        

Current Status: Despite clear evidence and community pressure since August 7, 2025, Elegoo has only provided generic support responses stating the issue is "under review by R&D."

🔍 Technical Evidence

Community investigation by user Sims (HACC) revealed multiple pieces of evidence through detailed binary analysis:

DSP MCU Firmware Analysis

The DSP (part of Allwinner SoC) uses Xtensa architecture and runs as the mainboard MCU. Binary analysis shows:

Clear Klipper MCU code paths in the DSP firmware
Xtensa architecture not supported by mainline Klipper—proving custom modifications
Firmware is not stripped, allowing detailed reverse engineering

Bed MCU Firmware

Contains commands not present in mainline Klipper
Mainline Klipper can connect but shuts down due to version mismatch
Reveals exact commit: 616 commits past v0.9.1 (shorthash 28f60f7e)

Host Software Analysis

Main application at /app/app is written in C++
Contains transpiled Python code from Klipper's Klippy host
Original references to Klippy remain intact in the C++ version
Includes components like mem_interface_DSP

Embedded Web Server (Mongoose 7.12)

Firmware exposes an HTTP service identifying as Mongoose/7.12 (embedded web server).
Mongoose 7.12 requires a commercial license to be able to distribute it without publishing code, which ELEGOO does not have.
If no commercial license was obtained, this is a separate license violation in addition to any GPL obligations.

Sources: Cesanta Mongoose, Licensing, Firmware evidence link pending

Network Traffic Investigation

Community members investigated excessive network usage:

For more details, see the note below.

Printer generates 70GB+ of traffic per month while idle
Health checks ping servers 10+ times per minute
Traffic analysis shows connections to Apple servers
Responsible for 29.5% of household network traffic while idle

Technical Note: While open-sourcing may be challenging due to Allwinner and Chitu involvement, other manufacturers like Creality have solved this by releasing source code alongside binary blobs for proprietary components.

Security Concern: Running known out-of-date open-source software without access to security patches creates significant risks for botnet exploitation.

🏢 Industry Context

Unfortunately, Elegoo isn't alone in problematic practices. Some vendors have GPL compliance issues; others impose ecosystem restrictions (not GPL violations):

Anycubic: KobraOS on 2.x and 3.x series violates GPL on multiple libraries including Klipper
Chitu-supplied platforms: Shared firmware stacks used across brands (e.g., Anycubic; some Creality models historically) have, in some cases, resulted in distributions missing the corresponding source for modified GPL components. Supplier contracts do not remove the distributor’s GPL obligations (GPL‑3.0). Chitu Systems' firmware and hardware are proprietary, which can constrain user modification and repairability (context).
Historical cases: Community reports cite GPL gaps on specific models (e.g., Creality CR‑X), while other products later published sources (e.g., Creality K1 series).
Marlin/Linux derivatives: Some vendors have shipped modified Marlin, Linux kernels, or Entware without timely source publication. GPL‑3.0 requires providing complete corresponding source to users of the binaries.

          The Solution: The 3D printing community needs to
          hold manufacturers accountable. GPL violations harm innovation,
          security, and user rights across the entire ecosystem.
        

Vendor statement: “No, the ELEGOO OS is not based on Klipper. The Klipper solution uses a dual-chip setup, consisting of an SOC + MCU, whereas the Centauri Carbon’s hardware architecture uses only one chip. Currently, it is not compatible with open-source Klipper commands or some open-source plugins, such as Fluidd.” (Hackster, Feb 17 2025) (source). This page aggregates community technical indicators of Klipper‑based components and modifications. If confirmed, GPL‑3.0 requires providing the complete corresponding source to users of the distributed binaries (GPL‑3.0).

⚖️ Legal and Policy Points

Recent discussion clarified several important GPL topics and consumer options:

Binary blobs vs. GPL‑3.0: Linux allows some blobs under GPL‑2.0 with exceptions; GPL‑3.0 requires complete corresponding source for modified GPL components. A blob cannot replace modified Klipper source.
Why compliance matters: If a vendor cannot publish changes due to third‑party contracts (e.g., Allwinner), they should not have used GPL code. Non‑compliance voids distribution rights.
Fraud and consumer protection: Misrepresentations (e.g., denying Klipper use) may create consumer fraud exposure; some users consider FTC/state reports.
Chargebacks (use cautiously): Some banks may accept disputes for deceptive practices. Risk: loss of support or future purchases.
International enforcement: GPL has seen international enforcement, including in China. For imported hardware, U.S. courts can issue border injunctions.
Chitu involvement: Community‑reported analysis suggests Chitu involvement with similarities to Anycubic Kobra 2 Pro (community analysis, repo). Where possible, prefer primary evidence (firmware strings/diffs, vendor docs). This informs where to direct compliance requests.
Mongoose 7.x licensing: The Cesanta Mongoose embedded web server (v7.x) requires a commercial license for proprietary firmware; using it without one would be a separate license violation. Not to be confused with Mongoose OS (a different product with a Community Edition under Apache‑2.0). See licensing.
Complete Corresponding Source (CCS): Publication of a repository is a start; compliance requires the complete corresponding source for distributed binaries, including build scripts and instructions sufficient to reproduce the firmware. Community is reviewing the repo for CCS and any licensing (e.g., Mongoose 7.12) coverage.

These points reflect community discussion and are not legal advice.

✅ Good Actors (Embracing Open-Source and Community)

These companies often contribute to the broader 3D printing ecosystem, foster innovation, and empower users with flexibility and control.

Prusa Research — PrusaSlicer; strong community engagement and documentation.
LulzBot (FAME 3D) — Historically 100% open‑source; robust printers that encourage user modification.
Creality — Released open-source Klipper firmware for K1 series and Ender 3 V3 KE.
Ultimaker — Long-standing open-source ethos; early printers released with open designs.
BCN3D — Published original design files for Sigma/Sigmax R19 to benefit the community.
Rat Rig — Open-source V‑Core series; open hardware approach encourages modification.
Sovol — SV08 project sources published on GitHub.
Snapmaker — U1 runs Klipper; FAQ states commitment to publish sources (FAQ).

If you have more examples, propose additions via PR or message in the thread.

🤝 Community Support

The community has rallied behind this issue with overwhelming support:

50+
Discord reactions

25+
Active community members

Multiple
Email requests sent

100%
Community agreement

Notable Community Quotes:

Lamarc | N4 | CC (HACC): "Everyone including elegoo is required to stick to licensing rules. It's clearly Klipper under the hood so it has to be made available"

Anna | DevMiner (HACC): "Taking opensource projects (Klipper) and calling them your own is super scummy"

Anna | DevMiner (HACC): "If you take opensource software that's licensed under GPL-3.0, modify it and then not allow people to see the code, you're violating the license and are very easy to sue."

leiden6665: "Yeah, any derivatives of Klipper have to be open source because of the license. I mentioned this in one of the other chats I'm surprised it took this long for someone to bring it up."

zuturiddu: "I fully support this request, which is essentially asking to adhere to use of open source software under a specific license."

Fabrizio | N4: "I support this. Provide the source."

bloky246: "I hope they make it open source as well"

Connor: "I stopped having the printer from idling anymore and now I'm gonna just turn off the wifi, the Chinese have too much to gain from my american network until they can explain themselves"

brando753: "GPL compliance is simple: if you use GPL code, you must provide the modified source on request. If you cannot, you must not use GPL code. Providing binary blobs is not compliance. Next step: document refusals and contact SFC to support enforcement."

🙏 Special Thanks to Our Contributors

This community effort wouldn't be possible without the dedication and expertise of numerous individuals. We extend our heartfelt gratitude to everyone who has contributed to this important cause:

This is what open-source community looks like: Technical experts, concerned users, and advocates working together to protect everyone's rights. Every contribution, from detailed technical analysis to simple support messages, has been valuable in building this case.

🔬 Technical Analysis & Investigation

Sims - Initiated the request for Elegoo to release their modified Klipper source code, providing detailed technical proof from the firmware binaries showing modifications to the MCU, bed MCU, and the transpilation of Klipper's Python host code to C++. Discovered evidence the firmware was based on Anycubic's and found articles where Elegoo explicitly denied using Klipper.
Rabir - Verified that mainline Klipper could connect to the printer's bed board, confirming the specific version and commit Elegoo was using.
motorhead1991 - Pointed out usage of other open-source projects like the Linux kernel and Entware, implying further license obligations.

✉️ Active Advocacy & Communication

bloky246 - Emailed Elegoo directly about the open-source request multiple times and shared the canned responses with the group to keep others informed of the official (non)progress.
Anna | DevMiner - Consistently pushed for the source code release, created a separate channel to move the off-topic network traffic discussion, and regularly pinged Elegoo staff for updates. Also sent emails to support.
beiyr - Actively pinged Elegoo staff for updates, contacted the creator of Klipper to inform them of the situation, and attempted to contact the firmware developers (Chitu) directly.
EXEN - Voiced support, actively pinged Elegoo staff for updates, and created a Reddit post to raise broader awareness of the issue.
lilybwees - Articulated the community's position clearly, arguing that Elegoo had a legal and ethical obligation to release the code, especially since they had lied to reviewers. Defended the community's persistence when moderators intervened.
brando753 - Provided a detailed explanation of GPLv3 license compliance, refuting the idea that binary blobs or "cleaning up the code" were acceptable. Argued that Elegoo's actions constituted fraud and suggested contacting the SFC and the FTC.
ViciousNarwhalFL - Suggested adding the issue as an article on Louis Rossmann's consumer rights wiki to increase public pressure.

💪 Community Support & Awareness

Lamarc - Voiced early and consistent support for the request, emphasizing that all parties, including Elegoo, must adhere to licensing rules.
Delulu Delilah - Expressed 100% support for the open-source request.
zuturiddu - Supported the request, framing it as a simple matter of adhering to open-source license terms.
leiden6665 - Noted early on that derivatives of Klipper must be open source due to the license and expressed surprise it took so long for the issue to be formally raised.
coffeecup - Added their voice to the call for Elegoo to provide the source code.
Fabrizio - Supported the movement and demanded the source code.
nate™ - Co-signed the request.
harrym - Expressed that the printer would be even better with access to the open-source Klipper software.

🌐 Network Traffic Investigation

crazyantihacker - First raised the issue of the printer's excessive network traffic, reporting that his device had uploaded over 70GB in a single month while idle and linked to a Reddit thread discussing it.
Marcel - Provided screenshots from his network monitoring tool confirming the excessive data usage.
LA3QMA-KGB - Used tcpdump to investigate the traffic, noting that the slicer software also generated significant traffic.
Kvviingu - Analyzed his network traffic, confirming that the printer was responsible for a large percentage of activity even while idle and that it was mostly a high volume of health checks.

📚 Industry Context & Legal Insights

Corey Stup - Pointed out that Anycubic engages in the same practice of violating GPL with their KobraOS, providing industry context.
baconmilkshake - Argued that the situation was more likely due to a rushed development process rather than conspiracy, but highlighted the security risks of running outdated, closed-source software and the potential for creating a botnet.
erica - Downplayed network traffic conspiracy theories but emphasized the seriousness of the legal and ethical violation of the Klipper license.
Tyler - Suggested that Elegoo's staff might be unaware of the Klipper usage, with the firmware being handled by a third-party board manufacturer, and mentioned that US state departments of justice could be interested in the case due to deceptive advertising.
Louis - Offered the perspective that Chinese companies have historically had less respect for open-source licenses and that marketing likely denied using Klipper because the implementation didn't meet user expectations for a full Klipper-based product.

Special Recognition: Owen (Technical Support) from Elegoo deserves credit for being the only Elegoo employee to acknowledge the issue directly and provide a timeline, showing that constructive dialogue is possible.

Community Moderators & Platform Providers:

YogurtDrink | Resin / CC - Clarified community roles and helped direct requests to appropriate Elegoo employees
Chirimorin | CC, N4Pro, S4U - Provided context on network traffic analysis

To everyone listed above and the many others who have supported this effort: Your collective voice has turned a single technical observation into a powerful community movement. This is exactly how open-source communities should work—together, transparently, and with respect for the legal frameworks that protect everyone's rights.

📧 Elegoo's Response

Community members have received mostly identical canned responses from Elegoo support, with multiple people reporting receiving the exact same message:

Typical Canned Response:

Subject: Re: Request for GPL Compliance - Centauri Carbon Firmware Dear Customer, Thank you for providing us with your valuable reply. We greatly appreciate your input, and we want to assure you that we are actively working on addressing the issue you raised. Currently, we have submitted the relevant information to our Research and Development (R&D) team and are awaiting their response. However, we regret to inform you that there has been a delay in the process, which has contributed to the extended timeframe. We sincerely apologize for any inconvenience this delay may have caused you. Please rest assured that your feedback is important to us, and we are fully committed to resolving the matter as promptly as possible. Our R&D team is diligently reviewing the information and exploring possible solutions to address the issue you encountered. Regards Jett Yue ELEGOO Support Team

— Multiple community members received this identical response

Community Reactions:

Marcel | CC (HACC): "Got the same response 1 to 1"
erica: "yeah, i got this exact same response too"
Anna | DevMiner (HACC): "they just have canned responses to all the common issues"
Anna | DevMiner (HACC): "I'd be great if elegoo can get their head out of their butt and have the courage to talk like real people and not just copy-paste the same message"

          Staff Response: Owen (Elegoo Technical Support) acknowledged the issue and mentioned there "should be a response in a day or two" as of August 12, 2025. However, no concrete action has been taken as of the latest community reports on August 27, 2025.
        

Community Concern: Multiple members expressed frustration that Elegoo employees (including moderators) were unable or unwilling to directly address the technical GPL compliance issues raised by the community.

🆕 Latest Updates

Clarified: binary blobs are not a GPL‑3.0 workaround; complete corresponding source is required for modified Klipper.
Community notes potential fraud concerns from past denials; some consider FTC/state reports.
Some users weighing chargebacks; caution: this can impact future support/purchases.
Discussion on international enforcement and possible border injunctions for non‑compliant imports.
Chitu involvement likely; similarities to Anycubic Kobra 2 Pro firmware observed (community analysis). Prefer primary evidence and add dates where possible.
Links added: Reddit context, Hackster review, OctoEverywhere mention, Rossmann wiki suggestion.
Workarounds: Raspberry Pi host possible via serial‑multiplexer, MCU side remains challenging.
New Reddit thread highlights: broken WebUI during prints; reports of thermal‑runaway risk on 1.1.25; excessive network traffic; community demand for source to enable community fixes and OpenNept4une‑like progress; confirmation that Klippy is transpiled to C++ and modified.
Examples cited: router blocking as workaround for telemetry; precedent that Creality released Klipper‑based sources for K1; acknowledgment that third‑party developers (e.g., Chitu) may be involved, which does not remove GPL obligations.
New: Evidence of embedded Mongoose/7.12 web server in firmware; the Cesanta Mongoose library (v7.x) requires a paid commercial license for proprietary use. Add primary evidence links. Note: not Mongoose OS.
New: ELEGOO published a GitHub repository for Centauri Carbon (link). Community verification in progress for GPL‑3.0 complete corresponding source (including build scripts) and any Mongoose 7.12 licensing.

📢 What You Can Do

If you own a Centauri Carbon, care about open-source rights, or want to support legal compliance in the 3D printing industry, you can help by politely but firmly requesting Elegoo release the source code.

Email Elegoo Support:

Use this template to contact Elegoo directly. The more people who reach out, the more likely they are to take action:

Subject: Request for GPL Compliance – Centauri Carbon Firmware Dear Elegoo Support Team, I am writing regarding the Elegoo Centauri Carbon 3D printer and its firmware's GPL compliance obligations. BACKGROUND: It has been conclusively determined that the Centauri Carbon firmware is based on Klipper (commit 616 past v0.9.1, shorthash 28f60f7e), which is licensed under GPL-3.0. Community analysis has revealed: • Modified DSP MCU firmware with Klipper code paths • Custom bed MCU firmware with non-standard commands • Transpiled Klippy host code (Python to C++) with original references intact • Version strings that confirm the exact Klipper commit used LEGAL REQUIREMENT: Under GPL-3.0, all modifications to licensed code must be made available to users. This is not a request—it is a legal obligation that applies regardless of business preferences or technical challenges. REQUEST: I respectfully but firmly request that Elegoo immediately release the complete modified source code for: 1. DSP MCU firmware (Xtensa architecture modifications) 2. Bed MCU firmware with custom commands 3. Host-side Klippy code (C++ transpiled version) 4. Any other GPL-licensed components used in the system PRECEDENT: Other manufacturers like Creality have successfully handled similar situations by releasing source code alongside binary blobs for proprietary components where necessary. I expect a concrete timeline for source code release, not generic "under review" responses. The 3D printing community is watching how Elegoo handles this legitimate compliance request. Thank you for your prompt attention to this legal matter. Sincerely, [Your Name] [Your Contact Information]

Other Ways to Help:

Share this page with other Centauri Carbon owners
Join the discussion on Reddit, Discord, and 3D printing forums
OpenCentauri community: Read the docs and join the Discord
Support open-source alternatives like mainline Klipper
Consider manufacturers who properly respect open-source licenses when making future purchases
If refusal persists, document responses and evidence and consider contacting the Software Freedom Conservancy about GPL compliance. For consumer deception concerns, some users are also reporting to the FTC/state agencies.
Chargebacks (last resort): Some banks may accept disputes for deceptive practices. Be aware this can affect future support or purchases.
Review the released repo: Inspect elegooofficial/CentauriCarbon for complete corresponding source (including build scripts) and any Mongoose 7.12 licensing coverage; open issues if gaps are found.

🎯 Expected Outcomes

If Elegoo complies with the GPL license (as they legally must), users will gain:

Security updates: Community can patch vulnerabilities
Feature improvements: Open development enables innovation
Hardware longevity: Continued support even after EOL
Transparency: Users know exactly what's running on their devices
Learning opportunities: Study and understand the firmware

Consequences of Non-Compliance: GPL violations are legally enforceable. The community has both the right and standing to pursue legal action if necessary, though everyone hopes Elegoo will simply do the right thing voluntarily.