If your code is GPLed you impose a cost on someone else to use it. Whether or not that cost is morally justified is not the point of the objection. I am making no judgment as to the righteousness of the goal of using a GPL or similar license.
By using a GPL you strictly limit who can consume your code to those who are willing to be bound by your views on what is right.
In this way (and limited explicitly to the scope of topics I am directly addressing in this comment), GPL licensing is similar to proprietary licensing: limits are imposed upon consumers of your code based on your licensing decision.
Again, I am not making a moral judgment or normative statement about what is good or right when it comes to code reuse or copyright in general.
Licenses which do not impose requirements upon consumers of the product are more free in the sense of allowing more behaviors, or placing fewer restrictions.
To me the key distinction is one of code freedom vs human freedom. Is the code free from malicious tampering or is the human free to make decisions and take action unhampered by another?
If I may quote the late Milton Friedman, "Heaven preserve us from the sincere reformer who knows what's good for you and by heaven he's going to make you do it whether you want to or not. That's when the greatest harm is done."
P.S. This is not an observation about you, because I don't know you, but I think we can observe the amount of hedging and defensive posturing I've taken by default in this response is illustrative of the type of response I can expect, based on observing similar discussions across various fora online. I hope that in this case that defensiveness was not necessary (:
What you describe seems to me exactly what John Locke said about Freedom of nature vs Freedom of people.
Freedom of nature is to be under no other restraint but the law of nature. Freedom of people under government is to be under no restraint apart from standing rules to live by that are common to everyone in the society
A license which enforce a share-and-share-alike system is to me much closer to freedom than if it allowed everyone to do what he likes, to live as he pleases, and not to be tied by any laws.
The basic division is negative rights vs positive rights, or at least that's how I frame it internally. A negative right is, very simplified, a right to be left alone. A positive right is a right to a specific item/privilege/behavior.
I think the wikipedia article[0] sums it up better than I can:
> positive rights usually oblige action, whereas negative rights usually oblige inaction.
There's some nuance between "do whatever you want" and "do whatever you want so long as it doesn't fuck with someone's day."
I'd really recommend the wikipedia article for a better treatment than I have time to give the discussion right now.
I'm actually not taking a position, but trying to help provide nuance in a debate that often teems with zealotry, and do so in a reasonable manner to provoke thought rather than vitriol.
My unexamined default inclination would be toward a BSD or MIT style license than a GPL. You may infer what you like about my default leanings in other areas if you like.
I've not given enough thorough thought toward software copyright to have a strong opinion as to the morally right position. This is not to undercut my comment and the observations I made above, but to make clear my standing which is ambivalent. I can certainly understand both sides of the argument and respect the position people speak from for either (to be explicit, the poles of the continuum being public domain on one end, with MIT/BSD licenses leaning far that way and hardcore copyleft on the other with GPL being the canonical example toward that end).
Toward the Friedman quote, that was not an attempt at appeal to authority to discredit the idea of copyleft, but an observation about the type of person (or at least the general tone of argument) who most vocally defends GPL licensing. If anything it was an appeal to authority to please be thoughtful about how to respond to my comment, and more to the point of why I included it, because it popped into my mind while responding.
This is a long-winded non-answer so far.
Really, what I was trying to do was to emphasize that there are costs to a GPL license, and that a reasonable person may think of those costs as such and not as freedoms. If you look at my response to a sibling comment, I'm thinking about this in terms of negative vs positive rights.
Looking at Friedman, I would certainly characterize him as someone who leans toward defining negative rights as freedom/liberty and positive rights as limitations thereupon. I would also characterize myself as leaning that way (so maybe I'm attributing my own views onto him). This is not to imply you are a hypocrite or declare that it is right or in any way argue against a GPL copyright in general, but just an observation.
With copyright (unlike patents), when I offer some code under some conditions, to first order I haven't subtracted anything from you -- you're free to ignore my code, maybe write your own. This isn't so different from offering you a banana for a buck, or a free bench in the park provided it carries a memorial plaque to my grandfather.
I used to default to the MIT license, basically saying "just don't be a dick about the authorship or the non-warranty". Over the years many companies, like Apple, incorporated this sort of software into platforms and products that circumscribe my freedom -- products that I "own" but can't legally control. The GPL (especially v3) is a compact of people building an alternative to this locked-down world. Closed platforms seem to me a much greater, and increasing, encroachment on our freedom in practice than the inability to legally incorporate GPL code into closed software. Both of these restrictions, closed-only platforms and open-only code, are things someone is choosing to offer and you are choosing whether or not to use -- I don't see a difference re: positive or negative rights, technically. (But I'm not super-interested in rights-centric political theory.)
Also, do you think that Linux, for example, is draining the world's resources? If so, how?