I've browsed through the Hurd faq, but I'm still not clear exactly what advantages Hurd has over the Linux kernel. The FSF say that when they decided to continue Hurd development in 1990 once they heard about Linux, Linux was not portable and didn't scale well (esp. to multiprocessor machines). That's not true anymore (although maybe the Hurd can do it better?).
The Hurd uses the Mach microkernel: microkernels are supposedly more efficient, but somewhere I read (I vaguely think it was by Linus, arguing with Tanenbaum about whether Minix was superior to Linux) that in the Real World, microkernels aren't as superior to monolithic kernels as they are theoretically supposed to be. Also, loadable modules give Linux some of the flexibility of microkernels. If anyone's keen to enlighten me/us on the intracacies of operating system kernels, they might like to comment on cached microkernels, like what the freedows project uses (www.freedows.org), or what the essential differences are between the Linux and BSD kernels. Andrew Tarr "If you're not part of the solution, you're part of the precipitate"
