I want my code to be usable by anyone developing free software of their own. I want them to be able to integrate it, modify it, redistribute their modified copies, and more.

The GPL, being long and complicated (over 5000 words, and that’s just the GPLv3!), and with the ideological restrictions built in, is incompatible with many widely used free licenses, not least previous versions of itself. In any situation where social or legal barriers prevent the target audience from switching to the specific version of the GPL in question, any code I release under it is unusable to them.

Releasing my software under a simple, understandable, and permissive free license prevents this from ever happening.

I dislike proprietary software. I don’t use it or create it, and advocate against it wherever I can.

But given the choice between letting some Chinese featurephone developer use my code without “giving back,” and preventing swaths of the free software community I care about from using and improving my code for themselves, I will favor permissiveness every time.

Because you are actually free to do what you want with it, instead of free to do what someone else wants you to do with it.

Yes, you are free to close it up and sell it, but everyone else then isn't free to use your changes. "More friendly to proprietary purposes" is "less free".

It's kind of like arguing that a country where anyone can steal from anyone else with impunity is more free. Not when you consider the rights of the person being stolen from.

Just because some forks of a project aren’t free, doesn’t mean that the project itself isn’t free. Especially if the project, like much of the e.g. MIT-licensed code in the world, is “done” for all intents and purposes and there is no reason at all to fork, proprietary or otherwise. (This comes up in the context of pure algorithms code a lot.)

Also, even if a project is copylefted, people can still just do... exactly what they did here. Which, while different in the weak sense of “avoiding copyright” or maybe “avoiding patents”, in the context of systems code like this almost always results in the same code on both sides anyway. If the choice is between either giving the proprietary developers your code to use, or making them re-implement exactly what you wrote without your copy for reference—with no option for “they don’t implement it at all”—then exactly what is the point of choosing the latter over the former?

> Just because some forks of a project aren’t free, doesn’t mean that the project itself isn’t free

We aren't talking about non-free, we're talking about less-free.

> Just because some forks of a project aren’t free, doesn’t mean that the project itself isn’t free

No. The fact that there can be forks of the project that aren't open is what means that the project itself is less free than a project where all forks must be open.

> Especially if the project, like much of the e.g. MIT-licensed code in the world, is “done”

I don't consider this relevant to the argument at hand.

> then exactly what is the point of choosing the latter over the former?

Are you asking me what the point is of making something you don't want people to do hard for them vs making it easy?

That's not a good analogy. In this case, people aren't being stolen from, they are freely giving it away for someone else to do as they wish.

Additionally, "theft" as you put it, in this case, doesn't affect the original property owner.

Digital analogies to theft rarely are good, but this one is passable. The main point is that this license grants software freedoms, but then doesn't do anything to protect it - thus enabling middlemen (like most of us devs are, for most software we write!) to immediately strip those freedoms away.

Proclamations of rights aren't really useful if they don't have means for enforcing those rights are not taken away.

I wasn't using it as an example of being deprived of property, but as an example of how infringing on other people's freedoms leads a system to be less free than one that doesn't.

You have the freedom to create your own proprietary derivative, a freedom you lose with the GPL version of rsync.