I say good for you for asking for what you wanted, and I'm glad your ex-T accepted. I don't think there is anything wrong with post-therapy contact if both people want it. I think that if there is a "social consortium" or any other guideline that prohibits this kind of contact (which, personally, I doubt, as the spirit if not the letter of the law focuses on prohibiting sexual or financial or otherwise exploitative relationships), I don't think that a client can waive this. Whatever the rules are, it's the T's duty to follow them as part of her profession, so I would think you are safe from having to sign anything away.