Responsibilities for supplying source code and NDA's

[David Watson]

As a newbie to the intricacies of GPL I wanted to know if someone could 
clarify the following hypothetical questions for me.

1. Who is responsible for supplying source code for an application, 
which has been developed for a client using GPL code?
I know I would need to release the binary to the client with source, but 
what about request from others like the original author of the GPL 
code.  Would I forward these request to the client or would I have to 
support any request myself?

2. How would the scenario above be affected by an NDA?  If the client 
releases a binary only of the application where does this leave me.
 
Thanks,
 
David