Since several people asked me for the source code, I'm putting it here, available for download. It was developed on older versions of farseer and of Surface sdk, but I was informed it is still working under current versions. If you download and use it, please be so kind as to leave a comment.
I talked with the people responsible for Farseer about the possibility of having Surface was one of the platforms, but their response was:
genbox: "... I don't see Microsoft Surface being the next huge gaming platform in the near future. :) If I include it in the source tree, a couple of people might download it and have good use of it, but I would also have to maintain the code. Every time I change the API in Farseer Physics each change must be implemented into the samples too - We are simply too few people (and don't have the hardware) to maintain a huge selection of samples on different platforms."
