Although I have had no response to my query on source for W2TUIO, I have come across this great post from Martin Kaltenbrunner which outlines a library that does Surface-to-TUIO conversion which is part of something called Squidy. The website is at squidy-lib.de which is the website of a German university that have developed this library.
This library should ensure that applications developed for TUIO such as Flash based ones, can also be used on Microsoft Surface. It gives assurance to those that are developing apps that are tested on CCV based hardware that they can then be applied to Surface based platforms. The library is open source under the LGPL license and available from Sourceforge.
I’ve yet to use it in anger. I’ll report back to the forum on results of tests with it.