Generally, you should never sign an agreement you don't understand.
On the other hand, it is not unreasonable for them to ask you to sign a legitimate non-disclosure agreement, since in the course of the conversation your friend may have disclosed material proprietary information about the services or products to be offered by the business. This would be true even if you are not a beneficiary of the program and did not get paid.
However, your friend and his partner should have asked you BEFORE the conversation to sign the agreement. You could have decided then not to engage in the conversation and refuse to sign the agreement. But not to worry - THEY messed up, you did not.
From the facts you have indicated in your question, they can't force you to sign the agreement at this point.
Answered on Nov 26th, 2013 at 9:05 AM