After signing a Non Disclosure Agreement at a public meeting held to find writers to contribute to a project, I discovered, as I learnt more,that many of the "ideas" were already in the public domain and were not original at all. I wish to distance myself from this organisation (I have contributed some ideas to their project but am not employed by them nor have I received any payment from them) but they are now sending me unsettling correspondence which insists on my adherence to their NDA. I do not have a copy of the NDA I signed and have requested that they send me one - they have not done so. Can they insist on the validity of the NDA if they will not supply me with a copy? Also how can they use the protection of an NDA when the essence of the project it covers is not their intellectual property?

Many thanks