OpenVSLAM is derivative work of ORB-SLAM2 and must use GPLv3 license

[jdtardos]

Dear OpenVSLAM community,

I am Prof. Juan D. Tardos, leader of the ORB-SLAM team at University of Zaragoza, Spain. As you know, ORB-SLAM, ORB-SLAM2 and ORB-SLAM3 have been licensed under GPLv3 for their free use in open-source projects. In parallel, our University, as owner of the software, is selling commercial licenses to companies all around the world that want to use our software in closed-source products. This gives the best of both worlds, research labs can use it for free, and companies making money with our software have to share some of their profits with our University. As the software authors, that is exactly our will.

Recently we got aware of the existence of OpenVSLAM, thanks to a big company that was using it. After the termination of the oficial OpenVSLAM release, the company analyzed the problem and concluded that OpenVSLAM is in fact derivative work of ORB-SLAM2, and to be on the legal side, they decided to buy a license of ORB-SLAM2 from our University.

As authors of the software, and together with the University's IP office, we also have analyzed in detail the issue and our conclusions are:

1. There is no doubt that the original OpenVSLAM paper incurred in academic misconduct. They are using all the ideas in ORB-SLAM and ORB-SLAM2 papers without giving proper credit to the original authors. Some examples: using three threads for tracking mapping an place recognition, using the same ORB features for everything, fast keyframe insertion and removal of redundant keyframes later, building a covisibility graph and an essential graph, using local bundle adjustment based on the covisibility graph, doing pose-graph for loop closing using the essential graph, etc. Their paper only contains a generic citation to ORB-SLAM2, together with other SLAM papers that are totally unrelated to OpenVSLAM. So it's obvious that the OpenVSLAM authors were hiding the fact that their work was heavily based on ORB-SLAM. This went undetected as it was published in a software conference, and not in a robotics conference full of SLAM experts.

2. There is no doubt that OpenVSLAM software is derivative work of ORB-SLAM2. Just to be clear: we have compiled a significant amount of evidence that OpenVSLAM software was written based on ORB-SLAM2 source code, and not only based on the ORB-SLAM and ORB-SLAM2 papers. This evidence comes in the form of same graphical interface, many idiosyncratic code sections (things that could be programmed in tens of different ways, but are programmed in the same exact way as in ORB-SLAM2) and a few obscure bugs that are reproduced in the same exact way, some of them found by members of the community (thanks!!). Sorry, but the legal team in our IP office does not allow us to give more details because the information we have collected can be used as evidence in case of legal claims. Also here, it's pretty obvious that the authors of OpenVSLAM were hiding the fact that their software is derivative work from ORB-SLAM2. In fact, when their organization decided to cose the original repository, they suggested that to be legally safe, you should consider OpenVSLAM as derivative work of ORB-SLAM2.

For these reasons, we kindly ask you to change the license of this repository to GPLv3. It is totally false that you cannot do it, because people that contributed in good faith to the repository did that assuming a BSD license, and there is nothing in the BSD license that precludes to redistribute it under GPLv3.

But the oposite is true, the GPLv3 license of ORB-SLAM2 does no allow to redistribute OpenVSLAM, being derivative work of ORB-SLAM2, under BSD. If you continue under BSD, you would be supporting academic misconduct and open software misconduct, and you would be putting good faith users of your repository in risk of facing legal claims.

Yours sincerely,
Juan D. Tardos

[ymd-stella]

Thank you for your comment.
I have understood your intentions. I have some questions about the conclusions.

1. There is no doubt that the original OpenVSLAM paper incurred in academic misconduct. ...

It is a matter between ideas, and has nothing to do with licenses that protect expression. If necessary, it would be better to contact the original authors of OpenVSLAM.

2. There is no doubt that OpenVSLAM software is derivative work of ORB-SLAM2. ...

Obviously, there is no need to make all of OpenVSLAM GPL, and it should only be necessary to address the derivative work part. For example, the graphical interface using Pangolin can be extracted to an external repository and made GPL. Would you be able to provide the problematic part?

Sorry, but the legal team in our IP office does not allow us to give more details because the information we have collected can be used as evidence in case of legal claims.

It is acceptable not to disclose the details, but I think it is excessive to claim it for the entire OpenVSLAM. Please clarify the scope of your claim.

--

As a side note, some similarities in the order of variable declarations have already been discovered at #37 (comment). The discovery and elimination of other similarities is in progress in #239.

The basis for thinking that the derivative work part can be eliminated is also in your statement.

many idiosyncratic code sections (things that could be programmed in tens of different ways, but are programmed in the same exact way as in ORB-SLAM2)

If it really could be programmed in tens of different ways, wouldn't it be easy to eliminate?
(I just want to check for inaccurate wording and conclusions. Honestly, I suspect that the legal team of your IP office is making unfair proposals.)

--

I sincerely hope that the intentions of the authors of ORB-SLAM2 and the original authors of OpenVSLAM will be respected fairly.

[jdtardos]

Thank you for your comment. I have understood your intentions. I have some questions about the conclusions.

1. There is no doubt that the original OpenVSLAM paper incurred in academic misconduct. ...

It is a matter between ideas, and has nothing to do with licenses that protect expression. If necessary, it would be better to contact the original authors of OpenVSLAM.

That's why I separated it in two different points. This simply proofs unethical behavior in the OpenVSLAM paper and repository. They were copying our ideas and software and trying to hide it.

2. There is no doubt that OpenVSLAM software is derivative work of ORB-SLAM2. ...

Obviously, there is no need to make all of OpenVSLAM GPL, and it should only be necessary to address the derivative work part. For example, the graphical interface using Pangolin can be extracted to an external repository and made GPL. Would you be able to provide the problematic part?

Sorry, the derivative part is most of the software, the interface is just one example, and the idiosyncratic sections and bugs are just evidence that we have collected for our legal team. Except for a few added functionalities (some new camera types) OpenVSLAM is essentially a refactored version of ORB-SLAM2 source code, that was reprogrammed using ORB-SLAM2 source code from the beginning. It was never independently programmed from scratch, as the authors pretended and some of the community members seem to believe. Modifying it further or as you say "eliminating the similarities" would change nothing, the result will still be derivative work of ORB-SLAM2, as derivative work is transitive: if B is derived from A and C is derived from B, then C is derived from A. Please, read the GPL license or ask your legal team: if A is GPL, both B and C must be GPL. Some legal teams in US companies just forbid their engineers to even read any GPL source code to avoid any contamination. If you want a clean system, you need to start from scratch, without reading other's GPL software.

Here is my summary of the current situation:

• The authors of the original ideas and software (ORB-SLAM2) don't want companies to use their software in closed source products for free, and they chose to open-source it under GPLv3.
• The OpenVSLAM paper incurred in academic misconduct, and their software violated ORB-SLAM2 GPLv3 license.
• The authors of OpenVSLAM have recognized the problem by erasing their repository and warning potential users.
• They have not tried to remove the conflicting parts, because they know they are everywhere, and it would still violate the GPLv3 license. Again: ask your legal team.
• The only legal solution is recognizing ORB-SLAM2 influence into OpenVSLAM and changing it to GPLv3.

And here is the ethical issue: why would this community remove the proofs of the offense and give the software to be used for free in closed-source products, going further against the ORB-SLAM2 GPLv3 license? Please, think on it.

Yours sincerely,
Juan D. Tardos

[ymd-stella]

First of all, it is important to note that ideas (algorithms and architectures, etc.) are not protected by the GPL. Are you sure you're not misunderstanding it?

In this view, most of the things quoted from ORB-SLAM2 are ideas, and only some expressions are stolen.

If you want a clean system, you need to start from scratch, without reading other's GPL software.

This is strictly a misunderstanding. Do you know about Computer Associates International, Inc. v. Altai, Inc.?
There is precedent for eliminating areas of similarity through clean room design.

--

I am under the impression that you are trying to over-interpret and misuse the GPL. If you think I am misunderstanding it, please show me the reasoning behind it.

I am thinking of stopping the publication until this discussion is finished.

[ymd-stella]

An additional case: mimemagic has reverted from GPL to MIT by removing the GPL-violating parts.

jellybob/mimemagic#3

[ymd-stella]

Removed the code from the default branch and added a note in README.md that past openvslam must be used under GPLv3.

I am also working on the Unrelease process.
ros/rosdistro#31716.

[ymd-stella]

Now openvslam is GPLv3.
Can I ask you to disclose the problematic parts?

[jdtardos]

I sincerely hope that the intentions of the authors of ORB-SLAM2 and the original authors of OpenVSLAM will be respected fairly.

Seriously?. The intentions of us as ORB-SLAM2 authors are extremely clear:

• Give proper credit to all the intellectual contributions to our work. Please read our papers.
• Respect the license of all software we have used in ORB-SLAM2.
• Make our software free for open-source projects under GPLv3.
• Allow our University (by the way, a university paid by the taxpayers in Spain) to obtain economical returns from the closed-source uses of our work.

The intentions of OpenVSLAM authors seem to be:

• Hide the intellectual contributions of ORB-SLAM2 to their work. Please, read their paper.
• Violate the GPLv3 license of ORB-SLAM2, hiding that it is derivative work. Please, read their software.
• Give our work for free to closed-source companies under BSD.
• To date, no private or public apology has been given to us.
  Sincerely, I see nothing to be respected here.

If you cannot see the difference, sorry, but I will stop any further communication.

[ymd-stella]

Have you seen https://github.com/OpenVSLAM-Community/openvslam/blob/in-discussion/README.md?