I can't seem to find license agreement anywhere for the PSD's. Is there a license agreement so these PSD's can be used?
Safest bet - contact the author directly and clarify. You can find their contact info through Dribbble.
Personally when I find resources I'd like to use (mainly non print, commercially), I contact the authors directly and offer to buy a license. Everyone's pretty open and friendly.
I used http://www.stockfreeimages.com/terms.html recently, they have a clear statement of terms and each image download page has the copyright details on it; handy.
Disclaimer: I develop it.