Co-pilot might be helping others infringe copyrights

May 08, 2021

It finally happened - a billions-of-parameters next-word-prediction model is fine-tuned to predict code from comments1 and this finally sparks a debate about copyright, the ethics of big models and other related things. This debate is probably long overdue, considering that these big models can do things like write books, generate “realistic” images, generate music, presumably all in some sense with properties derived from the petabytes of training data used to fit the billions of parameters.

Anyway, GitHub freely admits that in “0.1% of cases”2, their code-from-comments prediction model, called Co-Pilot, will regurgitate its training data. And of course, in some cases, this is clearly a Bad Thing because you can do things like reveal personally identifying information or secrets for web applications that people have posted on the public internet without fully appreciating that it is, in fact, public. But that was obviously going to happen because the web is a messy mess of good things like Wikipedia, journal articles and cat videos, but also bad things like warez, password leaks and hate speech. The thing which people are up-in-arms about is the fact that Co-Pilot is GPT-3 fine-tuned on “publicly available source code” (presuambly the entire commit histories on public repos on GitHub). And some of that source-code is licensed under the GPL3 which doesn’t allow you to do just anything with the source-code, but instead imposes specific obligations on people who do copy and re-use it in certain ways, which we’ll get to in a minute. Now there’s something bordering on collective outrage that this product is going to start enabling mass-violations of the GPL.

To be clear, regurgitating GPL-licensed code and slapping an MIT license notice on it has bad optics and understandably leaves a poor taste, but its sort of like coaching a 4-year-old to say offensive things in that you actually have to put in some effort into making it do that - in this case, giving it exact same function declaration (float Q_rsqrt(float number)) and also a copyright notice that does not contain the author name, which, as you would expect, will reproduce the body of the GPL licensed code, then reproduce the MIT license notice because presumably most code on GitHub is licensed permissively, so that’s what is going to minimize the model’s expected next-token loss. If the tweet author compiled that code, then distributed only the object code, its quite likely that they’d be violating the original license, regardless of what Co-Pilot said that the license was, because, well, the author using Co-Pilot knew what they were doing when they did that. And this is entirely the point.

To understand what constitutes “infringement of copyright” you have to go back to understanding what copyright is. Now, I’m not acting as your lawyer here nor am I intending for people to use this as legal advice to justify or not justify their usage of Co-pilot internally. But I did receive some legal training and I’m relatively confident that there is at least an argument to suggest that this isn’t so clear cut. But compare copyright to other things that we have in the intellectual property regime. We only recognize property in intellectual output to the extent that it is necessary to have a “fair” economic system and people who put work into things can reap the fruits of their labour, but also without infringing too much on the intellectual freedom of everyone else. Patents, for example, give you a limited economic monopoly on your invention but a part of the deal is that you have to go through a long registration process and disclose your invention to everyone else on the registry. Once you’re done, you can stop others from using that invention even if they came up with it independently.

Copyright on the other hand is much more limited. It doesn’t restrict intellectual freedom absolutely, but rather it restricts what people can do with your work. Copyright, at its core, is the exclusive right to make copies of the work, which is a verb in relation to the work and not a monopoly over the information contained within. Making an infringing copy fundamentally requires copying which in turn requires some intention to appropriate. If I happened to feed bits into a random number generator and the resulting stream was something that happened to look like a hollywood movie - I’d probably be in the clear as long as there was no reason for me to believe that this was actually just a copy of an existing movie because it featured an ensemble cast of Leonardo DiCaprio and Nicole Kidman and whoever famous actors are these days. I would probably be copying The Avengers if I keep feeding random bits into the generator and eventually get lucky and generate something that basically looks like The Avengers even if the generated title was The Superheroes.

I think Co-Pilot is in a similar boat. If I engineer the inputs to Co-Pilot such that it generates what is know is extremely likely to be a copy of some GPL-licensed code, then I use that code in a way that violates the terms of the GPL, I’m quite likely to be infringing the copyright of the original author. If I happen to generate code that looks an awful lot like code that came from the kernel or from GNOME, then I’m at least on notice that I should check if this really is a copy before I use it in a way that might be infringing. But if I happen to generate code that looks novel and adapted to solving my particular problem and there’s just no way that a reasonable person in my position could suspect that it was a copy of something else, then I’m probably in the clear.

1 This isn’t exactly a mind-blowing advance. The GPT-3 paper lists CommonCrawl as a dataset source, which is basically petabytes of text, some of which contains source code. Indeed, even GPT-2 will autocomplete code that kind of looks like the kernel if you give it a snippit of comments from the kernel.

2 Its not clear to me how they got that number. User study? Random fuzzing?

3 Or APGL. Or MPL.

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Written by Sam Spilsbury an Australian PhD student living in Helsinki.