(couldn't qualify for prizes as we didn't submit to a category)
What it does
How I built it
The operating system is based on the open source OS.js project. We implemented a noVNC client to stream content to your browser window and simulate the feel of a real desktop application.
Challenges I ran into
The challenging part was understanding the VNC protocol and hacking it to work with the browser and a contained program (since we didn't want to spawn a bunch of VMs for 10 different applications).
Accomplishments that I'm proud of
We're glad to have pulled it through even though the majority of the project was spent on the small details, and we almost gave up multiple times throughout the night.
What I learned
The smallest problems are often the most frustrating.
What's next for Apps-in-Browser.js
Making it into a service (and open sourcing it). This would be useful to run portable versions of a sandboxed game that a dev wants to put out. This way people don't have to install the game to play a demo version.
Another useful feature would be building a Sublime Text/ iTerm clone using web technologies so that you could send your team instances of your code and work off the same desktop environment.