In previous posts I explained some ideas on possible Counterparty-ZeroNet integration.
A recent commit [1] allows site owners to use ContentManager.py to control access to content.
This makes it even easier to perform integration with projects such as Counterparty.
[1] https://github.com/HelloZeroNet/ZeroNet/commit/4efcfa8bf49a1d9ce9b6b8095b4cd92d30c70d74