I believe everyone should be able to audit & change the software they run, or hire someone else to do so.
That does not mean I don't believe in paying devs (paywalls, especially softpaywalls, seems like the best way).
And it does not mean I believe all software must be public for all to use, feel free to keep code for internal use or share your code only with your customers.
@alcinnz
Something that people don't seem to realize is that you can 1) sell FOSS software at all; and 2) even the strongest copyleft licenses don't make you release your code publicly, all they require is that you make the code accessible to the users of your software and that you can't prohibit them from redistributing the code you gave them if they chose.
@nytpu
Weird edge cases: both the Reciprocal Public License and the Sybase Open Watcom Public License do require the public release of modified code.
This kind of copyleft is so strong that it isn't Free Software anymore: Debian, Fedora, and the FSF have duly rejected both licenses. But for some reason they are accepted as Open Source by the OSI.
@alcinnz
My explanation for why FSF consider these licenses non-free is simple, since the person modifying the software for their own use and not distributing the software to third parties. There are no infringing on those third parties' four freedom there's no reason for them to release the source code.
As for Why X licensed is acceptable by FSF/OSI and not the other, it's not the first time nor the last. The best example of this is the Original BSD license AKA BSD clause 4 which is approved by FSF but not OSI, because of the advertisement clause. (I still considering Original BSD as the best BSD license)