I've found two significant problems with getting ProofBuddy to run on a GoDaddy.com server. 1 - If you're server is running Windows and doesn't have PHP installed you will see a file not found error. Instead of the server telling you what it really is doing, not letting you run the php file, it gives a 404 error. 2 - They also have restrictions set very high for PHP scripts. First problem is that safe_mode is on, which I think I may be able to get around eventually but not with full functionality (sepia conversion probably wouldn't work). The other issue is that they have 44 PHP functions disabled through their settings. Of these, 6 are critical for ProofBuddy to function, 1 is required to be able to send mail which is used in the user system and to send order information to you and your client, and 1 is helpful to lengthen the time the server will allow you to add files. And these may just be problems on their lower priced hosting plans. They do offer VPS and dedicated servers which almost certainly wouldn't have these restrictions, although I've never used one so I can't be sure. If you have any questions about this I've set up a thread in the forums or you can leave a comment here.

Edit - 1/4/2008
It looks like this may not be a problem anymore.  I've had several users report that they are able to install and run ProofBuddy on GoDaddy servers without a problem.