When Photosynth's mobile panorama apps (for Windows Phone or iOS) completes stitching a panorama it saves a flattened version of that panorama to the device's camera roll in JPG format.
You should be able to view that without issue in any image viewer on your desktop, but the results will be flat.
If you want to view the panorama interactively, then yes, your friend will need to create a Photosynth.net account and upload their panoramas to the site.
After that they can send you the link to the pano and all should be well.
Let me know if you have any more questions.