Linux is the kernel. There is more to an OS than that and the classification of what is an OS and a flavour of an OS is arbitrary.
"Different enough", I guess is the mark.
E.g. "Ubuntu is a reskin of Debian with spyware"
"Different enough", I guess is the mark.
E.g. "Ubuntu is a reskin of Debian with spyware"
Linux in that list is flavour, but that is also the same with BSD. BSD is the flavour and Free, Net, Open all come from BSD 4.3. And if we really want to push it, it also includes MacOS 10.
I was also surprised to see Sailfish OS, Meego and Maemo listed separate from Linux, but my guess would be that the list comes from the build system of curl. Everything that is its own build target is listed there.