I have now developed the OS!
Ok, it's not actually an OS. It's just a python script that runs on the raspberry pi when it boots, that let you use the screen as a file browser using the buttons.
You can look at the entire file system of the raspberry pi, using this script, and you can run python files by clicking on them. This will form the basis of the apps, but right now, I've only added a shutdown app.
I still need to do a few bug fixes, namely, I need to make the text bigger, but once I've done that, I'll develop apps to make it actually useful.
I've been programming it using vim in the terminal, but I'm planning to support micro terminal editor. It's a basic terminal editor with mouse support, so it should help beginners feel right at home - it's meant to be an alternative to nano.
I've got the source code at github, and it's written solely in python, since that it's simpler. However, if I can get the screen working in Java, I'll write some apps and in Java, since i'ts probably more appropiate.
I'll hopefully have finished improving the 'os' in about a week, and then I'l work on some apps, and maybe an app store.
Also, feel free to follow me on github, and be notofied whenever I do a new commit!