This isn't really terribly difficult to set up. Pick a decent distribution (Debian, Arch), or FreeBSD (my choice), and install it with as little as possible. We'll be installing, afterwards, only the fundamentals along with their dependencies. While avoiding extra packages primarily saves on disk space, things like cups and compiz start adding up in memory after a while, so we install only the minimum. Try to avoid installing X11 using the installer, as this tends to pull in all of the extra packages and dependencies and fancy desktops that we're trying to avoid. Do this in VMware Player or Virtualbox (both free) first, so that you don't waste your time on a spare laptop only to mess things up. Install these afterwards, once you have a working command line:
- chromium (or firefox)
- feh
- fluxbox (recommended for ease of use and for being lightweight)
- SDL_image, SDL 1.2, GTK+ 2, libGLU (Dwarf Fortress dependencies. GTK+2 will likely be pulled in by Chromium/Firefox, though.)
- xdm (if it's not included with xorg. Replace with Slim or something if you prefer. XDM/Slim don't install 30 odd dependencies that I don't want or need.)
- xorg
That's all you need. Use feh to set a suitably dwarven background. Make sure you've got the dependencies for Dwarf Fortress (and in the case of FreeBSD, enable Linux compatibility), install it into your home folder, and you have your "minimal Dwarf Fortress installation", with only 6 to 10 top-level packages installed. No desktop effects running, no unnecessary daemons running in the background slowing things down. It's even still usable as a desktop, assuming you install the other packages you might want. Add Dwarf Fortress and Chrome/Firefox to the menu in fluxbox. If Dwarf Fortress isn't working, try running it from the command line (xterm) and read what it says. Installing applications is really very simple using the command line. A few minutes googling (or just read the man page, that's what it's there for) to find out how to add DF to fluxbox's menu.
If you really want to get fancy, use .xsession to have a "dwarf" user that automatically launches Dwarf Fortress fullscreen on login, and logs out when the game quits. This will, of course, be slightly more complex than just adding it to the fluxbox menu.
Installing Dwarf Therapist will be a little trickier, as sane operating systems tend to frown upon craziness such as actively modifying a program in RAM externally. Use
this if you want it. Make sure you have the dependencies it lists installed.