If you don't want to checkout the code repository and compile it yourself with either the Arduino IDE, or the command line inotool, then download the latest one of these hex files (compiled firmware binary) and load it onto your arduino UNO or clone (tested on ATMega328p processors only)
You can load this hex file on your system if you have the arduino tools installed, specifically avrdude. You need to know what port your arduino is connected on (typically /dev/ttyUSB0 or /dev/ttyUSB11 on linux) On linux run the following:
avrdude -D -U flash:w:/PATH/TO/firmware.hex:i -C /usr/share/arduino/hardware/tools/avrdude.conf -v -p atmega328p -b 115200 -c arduino -P /dev/ttyUSB1
Adjust the port variable /dev/ttyUSB1 to suit your system.
The command for windows users should be similar, though use google for more information, or use the arduino IDE and compile from your own git working copy
Ardustim uses a serial interface to control it so you can use either a dumb erial terminal application or the Druid4Arduino application which will give you a friendlier menu driven interface, which you can get from http://flyingcarsandstuff.com/projects/druid4arduino/