Ubuntu uses the Linux kernel, which is a monolithic kernel with loadable modules.
Yes, Ubuntu is an operating system, that uses the Linux Kernel.
Yes. By default, Ubuntu has supported multi processing since Ubuntu 5, due to the default kernel that loads is and SMP kernel. In other words it assumes a system has multiprocessing. If of course you don't, there is no degradation in performance.
Ubuntu is a Linux distribution (as in a specific OS setup with the Linux kernel.)
Support for the Atheros AR81 family of wireless NICs is already built into the Ubuntu kernel.
Linux is only a Kernel (Operating System). Different Flavours of linux have different user programs on top of the same linux kernel. A high level example : Ubuntu has the user program(package) GNOME while Kubuntu has KDE, whereas both ubuntu & Kubuntu use the same Linux Kernel.
No, has iptable already enable in kernel.
Debian based OS based off Ubuntu 8.04. Slight kernel modifications. Said to be faster than Ubuntu.
The 32-bit Ubuntu desktop kernel is set to 8 cores. The rest are at 64 cores.
No. Ubuntu includes kernel modules for most Ethernet adapters. And since Ubuntu tends to be cutting edge, if it does not have a module for a particular device, one is unlikely to exist elsewhere.
Ubuntu is a community effort and does not have a single maker. It is a distribution that is an off-branch from Linux. Google for "Ubuntu" and "Linux" for more information.
Ubuntu uses the Linux kernel, which uses 1:1 process model, from wikipedia: "Threads created by the user are in 1-1 correspondence with schedulable entities in the kernel. This is the simplest possible threading implementation." It's possible that supercomputer flavors of Linux support other threading models, but since this question was about ubuntu I answer so.
Ubuntu is whole operating system, and thus is not composed of just source code. You probably want the source of the kernel, for which just type "sudo apt-get install linux-source-2.x.xx" Replace x'es with kernel version you are interested in, typically version of your kernel. Type "uname -r" to find out, example result: 2.6.35-22-generic For which you should type "sudo apt-get install linux-source-2.6.35" Or just install linux-source, which always contains the latest source code. I don't know where it will be installed, sorry :p For individual programs, look on their webpages.