> Industry modifications to FreeBSD and Minix (and maybe NetBSD too?) were never sent back upstream
The most popular software that was derived from (a number of predecessors and) FreeBSD, Apple’s Darwin, is free software, nobody stops anyone from taking code from there. In fact, quite a few FreeBSD developers are (were?) paid by Apple.
We only learned by accident in 2017 that Minix is deployed on the Intel Management Engine[1] and we don't know what it does. To this day we don't have the code for the Minix variant that it runs. This wouldn't be the case if Minix was released under GPLv2.
Sony also used FreeBSD in PlayStation 4[2] and to my knowledge their modifications have not been open sourced. I may be wrong though.
At least, the assumption that “nothing” was sent back is wrong. I agree that the BSD license allows to take the code and run away with it, but you don’t have to. In a way, that makes BSD more free than the GPL.
> At least, the assumption that “nothing” was sent back is wrong.
That is true, I should have phrased it more carefully.
> In a way, that makes BSD more free than the GPL.
Yes, BSD is a permissive license and GPL isn't. But the original question was whether GPL leads to more splinters or BSD.
I think that the copyleft nature of GPL leads to fewer "effective" splinters since good modifications can be merged into upstream, and what is left unmerged tends to be less important to the success of the parent project. This has helped Linux gain momentum and unfortunately hasn't much helped the BSDs or Minix. I would like to see the BSDs succeed but I suspect that the permissive license has been one of the impediments to that.
You might take code from there. But you cannot take code from OS X and add it to Darwin. And that is why I cannot just install Darwin and run it on my computers if I wanted to use e.g., network cards.
The most popular software that was derived from (a number of predecessors and) FreeBSD, Apple’s Darwin, is free software, nobody stops anyone from taking code from there. In fact, quite a few FreeBSD developers are (were?) paid by Apple.