That is all true but a couple of things.
What Kagi will write is probably more a Orion for XWindows which does run on Linux but I can't see (except the development resources needed which means this won't be done until after it is open sourced) why it won't run on BSD.
As for GNU/Linux yes that is true for the distribution but would Orion actually be using any GNU parts - the system calls are direct to the kernel, the compiler will probaly still be Clang - what GNU libraries does a GUI app use.
