We use C# (tested on Windows, not Mono) with OpenCV (for .NET).
To get started, there is all kinds of indentation issues in the codebase, fix those so you can get a feel for how all the code is laid out.
There is a need for more documentation, especially on how to get a SixthSense device working. Most of our documentation currently resides on the Github wiki, which is a good place to contribute.
We use tabs-as-spaces, with 4 spaces for identation. There is all kinds of identation issues, and we encourage people to fix those.
We are working on an Android port, but, it is nowhere near complete. We will have more details ready once we have developed some of the UI.
The current code only runs on Windows, under the CLR virtual machine (i.e. C#).
Java (Linux, Mac OS X, Android, etc.) Dhaivat: https://github.com/Poincare/sixthsense (see java branch)
If you are working on a porting SixthSense to a different environment (*nix, Mac OS X, Android, etc.) please list it here, with some kind of link to code.