> one thing to note is that the "copyleft" regime depends on copyright to work

The idea of copyleft doesn't. The particular implementation in our regulatory reality does, because RMS & others figured out how to hack a system typically used for rent-seeking and restricting innovation (thus lots of parties are investing money to preserve it), and use it for the opposite goal.

I don't know what this abstract "idea of copyleft" is, but the underlying principle behind the GPL could not be achieved without copyright. The GPL doesn't merely embody some notion of "right to repair" or "right to tinker." Its principle is to put the user on the same level as the original developer. It therefore requires not only source code, but source code in the "preferred form of the work for making modifications to it," plus everything required to build that source code:

> The source code for a work means the preferred form of the work for making modifications to it. For an executable work, complete source code means all the source code for all modules it contains, plus any associated interface definition files, plus the scripts used to control compilation and installation of the executable. However, as a special exception, the source code distributed need not include anything that is normally distributed (in either source or binary form) with the major components (compiler, kernel, and so on) of the operating system on which the executable runs, unless that component itself accompanies the executable.

A world where you could freely modify binaries and distribute the results would not provide the same freedoms that are essential to the GPL. Copyright is absolutely necessary to accomplish that goal.

The GPL also embodies the fundamental moral theory of copyright: "I created this thing, so I get to decide the terms on which you use this thing." The GPL doesn't just embody the idea that users should be free to do what they could in a state of nature. It is fundamentally predicated on the idea of enforced reciprocity.

> The GPL doesn't just embody the idea that users should be free to do what they could in a state of nature. It is fundamentally predicated on the idea of enforced reciprocity.

Only because reciprocity is prevented by default through copyright law. In the state of nature, I could not prevent you from modifying my published software, and you couldn't stop me from taking your published modifications and using them, or distributing around. GPL is crafted to create an enclave supported by copyright law, in which things behave similarly to the desired "natural state".

As for source vs. binary thing, I feel that if there were no restrictions on binaries, there would also be no reason to not release source code in the first place. This makes the source code aspect important for real-world GPL, but not necessarily a core issue for a hypothetical copyright-free world.

Your explanation is completely inconsistent with the stated rationales behind the GPL: https://www.gnu.org/philosophy/free-sw.en.html

> A program is free software if the program's users have the four essential freedoms: [1]

> The freedom to run the program as you wish, for any purpose (freedom 0). > The freedom to study how the program works, and change it so it does your computing as you wish (freedom 1). Access to the source code is a precondition for this. > The freedom to redistribute copies so you can help others (freedom 2). > The freedom to distribute copies of your modified versions to others (freedom 3). By doing this you can give the whole community a chance to benefit from your changes. Access to the source code is a precondition for this.

The FSF twice says that having "source code is a precondition" for the freedoms the GPL seeks to protect. And that makes sense. If what you care about is allowing users to "study how the program works" and "change it so it does your computing as you wish," mere freedom to reverse-engineer binaries is insufficient.

Indeed, your interpretation makes the first two freedoms meaningless. It doesn't infringe copyright to reverse-engineer programs for study, or modify them for your own use. You don't need the GPL to enable those freedoms. Those two freedoms only make sense if you read them to mean that users should be able to study and modify the program in the "preferred form" for doing so (i.e. buildable source code).

> the underlying principle behind the GPL could not be achieved without copyright. The GPL doesn't merely require you to let other people reverse engineer your binaries, it contemplates that the distributed source code will be in the "preferred form" for working on it. There is no way to enforce that provision without copyright.

Sure there is. The GPL just used copyright as a hack to enforce on a limited basis what the creators explicitly think ought to be a universal obligation not dependent on the use of some upstream content that imposes the rule, for which the natural enforcement mechanism would be for the rules to be in law directly instead of copyright. “Copyleft” essentially implies that—its twisting what proponents see as a bad law into a tool for approximating the nearly diameteically-opposed law they wish existed in its place.

Without IP how can you enforce copyleft? Someone could just take your code and modify it and distribute modified binaries without you being able to do anything.

Something contemporary American culture has entirely forgot is the principle of a right to repair.

Even in a post-IP world you can have it be law that anything sold must include its documentation, manuals, and thus in the case of software on the sold product, its source code.

The fact so few realize how grossly unjust it is that most products sold today not only are undocumented but are intentionally obfuscated to make repair nigh impossible in order to drive replacement is the origin of the problem, though.

It's even worse - this is something of a yesterday's problem. We have a growing trend of turning products into services, which not only prevents you from repairing things (which you now don't own), but also restricts ways you can use them and creates an aggressive form of planned obsolescence.

> Without IP how can you enforce copyleft? Someone could just take your code and modify it and distribute modified binaries without you being able to do anything.

You can, for example, reverse-engineer these binaries or develop binary patches (without IP laws, all of this becomes legal).

In the existing legal system you can't. But we could write laws that allow this to be a thing (i.e. instead of the current situation of "you have full control over who can copy/redistribute your IP" it becomes "anyone can copy/redistribute your IP but you are allowed to specify X criteria including the requirement to redistribute source code").

You wouldn't have to. Without copyright, it seems to me that everything becomes copyleft by default.

I could, for example, modify any piece of software I like, and legally distribute modified copies to others. Even if I didn't want to share my modifications with a larger community (or didn't want to do it for free), I couldn't stop it - someone else could do that for me. And as 'wolfgke points out, being open source doesn't matter much here.

> You wouldn't have to. Without copyright, it seems to me that everything becomes copyleft by default.

No, without copyright, you cannot force the other party to give you access to the original source code.

BTW: There does not seem to exist an open source license that tries to emulate "no copyright"/"no IP". I.e. the license allows reverse engineering of all binaries derived from it virally, create modifications etc. and perhaps allows to use patents; but the license does not give you the right to demand access to the original source code.

You argued upthread for reverse engineering. Binary is the source code, albeit in less convenient form. So maybe it wouldn't be strict copyleft, but close enough.

> Binary is the source code, albeit in less convenient form. So maybe it wouldn't be strict copyleft, but close enough.

Buddy, you must never have worked with a decompiler. To say nothing of the source file structure and comments that are lost along the way.

Instead we get tarball dumps with no change history.

Tarball dumps are OK. The GPL doesn't require change history. Although it can be quite helpful, it would be quite hard to define universally - what level of history is required? It could range from "every character typed" to "changes from the last public release", which is essentially what we have now.

GPL requires source code, which it defines as "the preferred form of the work for making modifications to it."

This prevents release of compilable-but-obfuscated code, or transpiler output, etc., or intentional removal of information required to build the software (though this clause causes GPL-compatibility issues with authenticated-build platforms).

The difference between sifting through tarball dumps and puzzling through binaries is essentially of degree, not kind. If there's a line to draw, perhaps it should have been at "intentional removal of information".

> Binary is the source code, albeit in less convenient form.

At least the copyleft defenders would not agree.

Employees can take source code with them when leaving a company and share it with others.

Not only plain old copyleft relies on copyright, but also the model of publishing code under the GPL and charging for a commercial license. I have used three such libraries in client work, and I absolutely love this model:

- We can audit software before buying

- We have the ultimate "right to repair"

- Open source/hobby projects can automatically use it for free (SAAS/closed source projects often offer this as well, but there's more friction)

And even if we are not technically required to upstream any patches that we make under the commercial license, the average engineering team will try to keep their downstream patches to a minimum, and the easiest way is to get them merged in the original GPL version.

Copyleft is a strategy to reach a specific goal in order to address a specific problem. It is not in itself the goal.

In order to ask if copyleft would still be an effective strategy in a non-copyright world we would have to ask if the problem would still exist and how it would look like. Then we would have to compare copyleft to other strategies to see which would be most effective.

Personally I think that if the anti-copyright movement would managed to gain enough political support to remove copyright then copyleft would not be the most effective strategy to gain the goals defined by software freedoms.

By "stealing" I meant literally taking their money, not using their art.