I don't think you "must pay for it with your changes," as in article 5, Conveying Modified Source Versions, it only says that the work must do the following:
- have a notice that you modified it,
- have a notice that the work is licensed under the GPL,
- be licensed under the GPL, and
- if the work has interactive UIs, it must display Appropriate Legal Notices.
It says nothing about contributing changes back, the only freedom it restricts is the "freedom" to restrict the freedom of others. It is like the whole "is prohibiting slavery reducing freedom" problem.
> in article 5, Conveying Modified Source Versions, it only says that the work must do the following:
You have to keep reading the entire license...
Section 6 of v3 begins:
You may convey a covered work in object code form under the terms of sections 4 and 5, provided that you also convey the machine-readable Corresponding Source under the terms of this License, in one of these ways:
a) Convey the object code in, or embodied in, a physical product (including a physical distribution medium), accompanied by the Corresponding Source fixed on a durable physical medium customarily used for software interchange.
<or several other functionally similar ways are options in the full text linked below>
How is that not needing to convey your source changes to those whom you distribute the object code?
It’s been there since v1:
Paragraph 3 of the v1 or v2 GPL is similar to section 6 of v3:
You may copy and distribute the Program (or a portion or derivative of
it, under Paragraph 2) in object code or executable form under the terms of
Paragraphs 1 and 2 above provided that you also do one of the following:
a) accompany it with the complete corresponding machine-readable
source code, which must be distributed under the terms of
Paragraphs 1 and 2 above; or,
I think we have a different view on the meaning of "pay with your changes." I take it to mean "you must send patches/pull requests/... to the upstream project," which isn't the case. Whereas, if my reading of your message is right (feel free to correct me if I'm wrong) you consider it to mean something like "you must make the changes you make public."
I personally wouldn't consider the second interpretation as "paying" for Free Software any more as I would consider having people publically criticise me as "paying" for Free Expression.
You only have to send your changes to anyone to whom you distribute the modified program.
If that’s upstream, then you have to offer them upstream. If that’s to someone else who then decides to share them upstream, that’s also something you can’t prevent.
If you don’t distribute the program, you don’t have to send your changes anywhere.
(My main point was your citation of only Section 5 was incomplete with regards to your obligations under GPL.)
> It is like the whole "is prohibiting slavery reducing freedom" problem.
Except there are dozens of incompatible (A/L)GPL (2,3) licenses alone and an uncountable number of minor modifications of the same. So you end up with the "freedom" not to share code between various GPLed projects because they all are slightly different flavors of free.
- have a notice that you modified it,
- have a notice that the work is licensed under the GPL,
- be licensed under the GPL, and
- if the work has interactive UIs, it must display Appropriate Legal Notices.
It says nothing about contributing changes back, the only freedom it restricts is the "freedom" to restrict the freedom of others. It is like the whole "is prohibiting slavery reducing freedom" problem.