Besides its use for the work flow for a single person developing an app I fail to see the case for this system.
Here's the use case I have in mind: let's say I'm a programmer extending a game [1] built on Undum [2] engine, together with a writer who is writing a story at the same time [3]
[1] The Play, A dress rehearsal gone horribly wrong, by Deirdra Kiai. http://squinky.me/theplay/
[3] Story file: view-source:http://squinky.me/theplay/theplay.js