I'm currently working on implementing full API functionality in C# right now. Basically, everything is done and tested by now, but I'm not at home at the moment, and the project itself isn't even documented yet, so the public release has to be postponed for a bit. My project is a Portable Class Library, so it could be utilized on Windows, Linux, Mac, Android, iOS, and even more platforms which are supported.

Regarding the API's specification: It's pretty straightforward to use, but there is also quite a lot of unneeded redundancy. For instance, "long", "short", "Market", "Limit", and "Stopentry" values could be replaced with numbers (thus, making them easily enumerable). Also, I don't think there should be response data included for edited positions, as they also seem to be redundant for me.

By the way, as the site grows, positions and orders should have alphanumeric IDs (8 characters should be enough) in order to make them easier to recognize. Or just simply make the IDs user-based instead of using global values.