Considering that curiosity is not willing to share it, my take is to not try to push him to it. It's his hard work and it's decision to make what he would like to do with his code.
To me, the best things that can happen with this project are these (in no particular order):
Learn more about the client itself: Even if it means that the code is not out there, just learning a lot about the client and how things work in the client is a great piece of knowledge. If curiosity is willing to share some of that, it would be awesome!
A client that is truly moddable/customizable: At the end of the day, what we all want is a client that is open to modding and allows custom artwork and actions to show up in the client. While having a closed-source might limit a lot of things, it is still possible to have a client that's vastly better than trying to hex-hack the official client to do have custom things built, IMO. I could be dead wrong here, but I see the potential.
Motivate other developers to build a client: Take this knowledge and learn to build another client. Who knows that other person might just release the source to the wild .