Hi Peter, in answer to your questions:
1) The files included with the two license types are the same with the exception of the Photoshop .psd files being included with the developer license. The .psd files are useful for web designers who may be looking to change the layout of the theme, as they contain all of the layout/color/size information (essentially saving time having to collate these yourself). In order to use the files though, you still need to have a knowledge of .css, so for anyone who doesn't have these skills, the files would likely not be of use. You can still customize the theme even without these files. If you purchase a standard licence initially, and then later decide you need the Photoshop files, you can always upgrade at a later time.
2) Yes that site is a great example of how someone can completely change the look of the theme to make it more unique. AppThemes does not offer customization services, however we do have a c
ertified partners page where you can find developers for hire. If you make contact directly with an outline of your requirements, they can provide a quote for the work. Thanks.