Yes, to all of those, though some take more work than others. It says a lot that "systemd vs init.d" instead of "systemd vs sysvinit" was there. The question

Yes, to all of those, though some take more work than others. It says a lot that "systemd vs init.d" instead of "systemd vs sysvinit" was there. The question is not about the ecosystem, though, but about the kernel itself. Yes, there are embedded vendors (mostly networking equipment, and especially routers) who violate the GPL by not complying, but generally speaking, hardware vendors who choose Linux publish sources. Those sources may not ever make it into mainline, but the device trees/drivers for embedded stuff does provide a reference for a cleaner, better implementation. Compare to FreeBSD for the Playstation's management layer. Where are the contributions for Cell support? Where are the patches Sony certainly needed to make for wifi and bluetooth? Where are the patches from Juniper for validated FIPS?