It is a commercial program which you must purchase. However, the version sold is an older build not compatible with WM6.1 -- for that you need a newer cab. The way to do this is to purchase the older version (Handango has it) so you have a legitmate license, then download a cab of a new build.
For a cab of newer build see this thread:
http://forum.xda-developers.com/show...ht=MSVC_US_PPC
Look at post 1, step 3.