Does the "forced response to a new suit" concept apply to both players in the Goren bidding system?
This answer should not be limited to Goren only, but should be a general guideline to most natural systems.

Whether a bid is forcing or not depends on whether the bidder (or sometimes his partner) is limited or not. In your example:


1S is forcing because responder has not a chance to show his strength yet. He can have a massive hand waiting to be shown on the next few rounds. 
For most pairs, 2C is not forcing, since opener is in some sense limited: he did not make a forcing opening, and he did not jump shift when given the chance to. Responder has the right to pass this bid if he decides 2C is the most suitable contract at that time.
2D is forcing, be it natural or artificial, again because responder's hand is still unlimited. Opener is bound to keep the bidding open.


Therefore the general rule is that responder's new suit bid is forcing due to an unlimited hand. For opener's non-jump suit bid, it is not forcing since his hand is limited, but this is still subject to partnership agreement.