The codepad server app (aka codeserver) is written in Clojure, so you will need to install a dependency management tool called Leiningen. This will also be used to compile the app. Start by downloading this script (just right-click and save into your downloads directory).
Once downloaded, copy the script into ~/bin. Create this directory if it doesn't exist.
cp ~/Downloads/lein ~/bin
Add this directory to your PATH environment variable by adding the following line to ~/.bashrc:
export PATH=$PATH:~/bin
Make the script executable.
chmod a+x ~/bin/lein
Run lein and it will download the self-install package.
Codepad's front-end application just consists of a single HTML file and some JavaScript. I know, not very exciting. So, just open index.html in your favorite browser. If you want, you could also run a local server to serve the files. Read more here.
Once you have Codepad in your browser, you'll need some kind of application (known as the codeserver) on the back-end which can handle the various requests that Codepad makes. For example, each time you type a character, Codepad sends a message to the codeserver to notify all other coders of the character that was typed.
By default, the Codepad page sends messages to the codeserver instance I have running at codeserver.us. Because of me being a noob when I wrote this, you'll have to change the string server_name in js/main.js to 'localhost'. Make sure to change it back.
To start running the codeserver:
cd codeserver/
run lein
If this is your first time running it, you'll see a few packages being retrieved and then it will just hang. This is good! It means its working!
If you're not developing features for the codeserver, don't worry about this.
In the codeserver directory run:
lein compile
lein uberjar
which will produce a standalone jar file for the server application.