Companies extend the BSD OSs with proprietary additions, then abandon the work and it gets lost. With Linux, everyone is forced to play nice and release under the GPL, and the work gets to live as long as people value it.
Hence the Linux kernel snowballing and taking over the world, whereas the BSDs have not, despite being at least as strong technically.
The better Linux gets, the more people target it, and the virtuous cycle continues.
Additionally, as it grows bigger and bigger, the more of the proprietary competition it crushes underfoot (sorry Solaris), and the more traction FOSS gets.
Companies extend the BSD OSs with proprietary additions, then abandon the work and it gets lost. With Linux, everyone is forced to play nice and release under the GPL, and the work gets to live as long as people value it.
Hence the Linux kernel snowballing and taking over the world, whereas the BSDs have not, despite being at least as strong technically.
The better Linux gets, the more people target it, and the virtuous cycle continues.
Additionally, as it grows bigger and bigger, the more of the proprietary competition it crushes underfoot (sorry Solaris), and the more traction FOSS gets.