The app is fairly new but it is open-source. It's a lot like Brackets and Atom.io than it is to Notepad++ though. I've requested Atom Editor before, but I'm now starting to realize that Atom might be a lot harder to make portable as in their forum, they're having a tough time as well.
I hope LightTable could be more easier to make portable...I hope. It is a very nice looking editor with a very nice set of customization to it.
You can check it out at: http://lighttable.com/
The source is also linked from the front page and housed on Git.