Our
certified partners can be selected based on various things, such as recommendations and feedback we have received from members of the community, the quality of their work, and our own experiences of dealings with them. Yes we trust them and their work, however essentially they are still independent contractors and as such, we can really act only as the referrer. If we were to receive complaints about a specific partner we would certainly review their status on our page. Of course using any of the certified partners is optional, and if you wanted to source your own developer elsewhere then this is entirely up to you.
The only difference between the standard and developer license is that the developer license includes the Photoshop .psd files.
The files are useful for web designers who wish to redesign the layout of the theme, as they contain all of the layout/color/size information for all of the pages used within the theme. You still need knowledge of .css in order to make use of the files, so if you do not, then you may not find a use for them. Thanks.
